Fender Deluxe Reverb Reissue Hoffman Board Conversion - The Basics

[eleventeen]

With your crimped slip-on connectors, pulling those AC-in and PT feed wires off the fusepost and running them under the fuse would be easy and I would recommend that.  And it would good to twist all those AC-line wires; the ones coming in from the power cord and the ones running back to the PT. Just as a point of "propriety" we like to see the black wire hit the fusepost first, the inside lug first. Then the AC line switch. That way, if the fuse blows and the amp is on your bench, there is one and only one item still connected to the AC line. As you have it wired, the AC switch under those conditions remains all the way hot. It's certainly less of a big deal with those insulated push-on crimp connects you are using and it affects utterly nothing but is a "best practice". I would try to get the black-white from the AC line and the black-white feeding the PT all in one 4-wire bundle. Twist or tie wrap. The raw B+ from the rectifier tube can also run in or along that bundle. Just for neatness, and it's also the idea that once you wire those fundamental elements, you should never have to touch them again.


I'd also like to see some sort of wire control on the HV and the 5V wires from the PT. A nylon "P" cable clamp is the usual way.

[Mike_J]

With your crimped slip-on connectors, pulling those AC-in and PT feed wires off the fusepost and running them under the fuse would be easy and I would recommend that.  And it would good to twist all those AC-line wires; the ones coming in from the power cord and the ones running back to the PT. Just as a point of "propriety" we like to see the black wire hit the fusepost first, the inside lug first. Then the AC line switch. That way, if the fuse blows and the amp is on your bench, there is one and only one item still connected to the AC line. As you have it wired, the AC switch under those conditions remains all the way hot. It's certainly less of a big deal with those insulated push-on crimp connects you are using and it affects utterly nothing but is a "best practice". I would try to get the black-white from the AC line and the black-white feeding the PT all in one 4-wire bundle. Twist or tie wrap. The raw B+ from the rectifier tube can also run in or along that bundle. Just for neatness, and it's also the idea that once you wire those fundamental elements, you should never have to touch them again.


I'd also like to see some sort of wire control on the HV and the 5V wires from the PT. A nylon "P" cable clamp is the usual way.

+1. Keeping the unfiltered AC or DC (red wire from the rectifier to standby switch) wires together and behind the power tubes will help you make a quieter amp. Would have your black and white OT primary wires tie wrapped together and run them between the power tube and rectifier tube if they are long enough.


Looks like your chassis has been painted? If so, you need to make absolutely certain that you have a good connection between the ground wires and the chassis, especially that green wire from the power cord. Never had a painted chassis before so don't know anything about them. Have some old Fender chassis with quite a bit of rust in them so the paint makes some sense. However, critical that the grounds are sound. May want to use emery cloth to get a clean ground point. Your red and yellow wires are adequately twisted but when you twist the green wires (heaters) I would make them tighter.
 
 
 Thought of another turret wiring point. Should press your component that a wrapped around the turret 180 to 270 degrees (wire, resistor, capacitor, etc.) towards the bottom of the turret for soldering.
 
 
 Keep taking pictures as you go. Easier to fix these items as you go along.
 
 Thanks
Mike

[davegardner0]

With your crimped slip-on connectors, pulling those AC-in and PT feed wires off the fusepost and running them under the fuse would be easy and I would recommend that.  And it would good to twist all those AC-line wires; the ones coming in from the power cord and the ones running back to the PT. Just as a point of "propriety" we like to see the black wire hit the fusepost first, the inside lug first. Then the AC line switch. That way, if the fuse blows and the amp is on your bench, there is one and only one item still connected to the AC line. As you have it wired, the AC switch under those conditions remains all the way hot. It's certainly less of a big deal with those insulated push-on crimp connects you are using and it affects utterly nothing but is a "best practice". I would try to get the black-white from the AC line and the black-white feeding the PT all in one 4-wire bundle. Twist or tie wrap. The raw B+ from the rectifier tube can also run in or along that bundle. Just for neatness, and it's also the idea that once you wire those fundamental elements, you should never have to touch them again.


I'd also like to see some sort of wire control on the HV and the 5V wires from the PT. A nylon "P" cable clamp is the usual way.

Ok fixed everything except cable ties - I'll have to find some of those.

Unfortunately the black/white pair from the PT isn't long enough to do anything except a straight line to the on/off switch.

[davegardner0]

Looks like your chassis has been painted? If so, you need to make absolutely certain that you have a good connection between the ground wires and the chassis, especially that green wire from the power cord. Never had a painted chassis before so don't know anything about them. Have some old Fender chassis with quite a bit of rust in them so the paint makes some sense. However, critical that the grounds are sound. May want to use emery cloth to get a clean ground point. Your red and yellow wires are adequately twisted but when you twist the green wires (heaters) I would make them tighter.
 

I don't see any evidence of paint on the chassis, it appears to be bare metal. I'll check the continuity to that new ground lug to confirm.

Keep taking pictures as you go. Easier to fix these items as you go along.

If you guys don't mind checking my work I'm happy to keep posting photos. Thanks!!!!! 

[eleventeen]

Better. I'd still remake the AC feed back to the PT from the sw/fuse and get those two out of the way, you'll be fighting it/them later when you go to wire up your 6V6 tubes. If it takes a splice or two, I'd still do it. Got some females of those crimp-on insulated connectors? Or just solder the splices together, heat shrink (or jacketing stripped from small diameter cable) with bigger jacketing, like the size of your AC cord, around both splices.


Really like to get wires you will never touch again out of the way, all the way out of the way.


Incidentally, if/when you make such a splice, offset the splices, don't cut the wires the same length.


sw----------X-------PT
sw-----------------------------X-----------PT




Not to harass you, just to point it out, you're still running the raw AC in black to the side terminal on the fusepost. Leave it alone, S'OK.

[Mike_J]

Looks like your chassis has been painted? If so, you need to make absolutely certain that you have a good connection between the ground wires and the chassis, especially that green wire from the power cord. Never had a painted chassis before so don't know anything about them. Have some old Fender chassis with quite a bit of rust in them so the paint makes some sense. However, critical that the grounds are sound. May want to use emery cloth to get a clean ground point. Your red and yellow wires are adequately twisted but when you twist the green wires (heaters) I would make them tighter.
 

I don't see any evidence of paint on the chassis, it appears to be bare metal. I'll check the continuity to that new ground lug to confirm.

Keep taking pictures as you go. Easier to fix these items as you go along.

If you guys don't mind checking my work I'm happy to keep posting photos. Thanks!!!!! 

Guess if I don't see rust on a Fender chassis I think it is painted. Not a bad idea still to use a little emery cloth under the ground connections to make sure you have the best connection possible in my opinion. Don't mind checking your work at all. Others have done so for me.


You can get cable ties from Ace Hardware. They aren't very expensive. I like the 4" GB ties part number 45-104. They work well for me. Also need some of the power cord clamps like Doug has in his Tube amp fuses, power cords and fuse section of his store. I would use them to firmly attach the wires to the back of the chassis so they are not in the way of the power tube wires. This was mentioned by Eleventeen and is very important in my opinion as well.


Thanks
Mike

[davegardner0]

Ok I added the splices to the PT supply side. Just need to get some cable ties and something to secure the wires to the side of the chassis. Also flipped the in/out of the fuse.



I started on the pots and jacks, got the bus bar on first. The Hoffman diagram shows a break between the normal and vibrato channel pots, is that real or just for diagram's sake? Also on the diagram on the right side of the bus bar it indicates ground, how is that attached? Another screw? Or is the pots bolted to the chassis sufficient grounding?



I attached the first shielded cable to the normal channel input jacks. It seems to not be physically anchored very well, is that okay? The braid is attached to one of the grounded points on the jack, and the hot is just floating, attached to those resistors. I guess I could tape the wire down where it will run under the turret board, that would really firm everything up.


Had a pretty funny moment trying to find the 1 Meg resistor for the input termination load. I wanted to verify I was reading the colors correctly on the resistors so I measured the resistor which I thought was 1 MOhm with my meter and I got something like 200 kOhms. After about 20 minutes of head-scratching and re-reading the color codes I realized I was actually measuring the resistance of ME, from my left hand to my right, since I was holding the leads on the resistor. Doh!!

[eleventeen]

That's the way it was done on Fenders. Of course, they used older style Allen-Bradley resistors (talking about the two 68K's) which had much stiffer leads than current types. You wouldn't have your question with the 68K-68K junction hanging in the air because with short leads it was quite stiff.


That absolute great thing about your 1 Meg measurement (and a hundred things like that) is that you'll never make that mistake again. Well, maybe you'll try to make measurements holding both leads, but you won't be fooled by your body resistance. That's one reason among many why we like to have an alligator clip or clip-lead on at least of your meter probes. Eg; "hands-free". Typically the black = ground. It also prevents one probe slipping onto a terminal it should not touch; causing a short or a meter blow or an arc-gouge out of your probe tip. It also kind of reminds you that you want to have only one hand dealing with the work when doing high voltage repair/test.


Wiring looks 10x better. Nice.

[sluckey]

The ground symbol on the right end of the pot buss wire is just to let you know it is ground. Don't connect that end of the buss bar to chassis.

RE: your input jack shielded cable...

I'd run the cable BEHIND those ground buss bare wires. Then lay it close to the chassis to run under your board to the socket, but don't tape or otherwise fasten to the chassis. (You may regret that later on.) They will be adequately secured like that. Here's a pic showing what I mean...

[Mike_J]

If you look at Sluckey's picture on the last post you will notice he did his buss bar a little differently than you did. The way you did yours, soldered to the back of the pots, is the way Fender did their grounds historically. That is how I did mine on my first few builds. Potential problem with it is every pot body is a chassis ground point.


If you notice on Sluckey's picture he has a buss bar that is NOT soldered to the back of the pots. Every ground from the pot connections and the circuit board go to the buss bar. The buss board is terminated at the input jack so there is only one preamp ground connection (in your case two, one for the normal channel input jack and one for the vibrato channel input jack). Don't know that you need to redo your buss bar as Fender did it that way for a long time but information for future builds.


Remember you need to install your grounds from the circuit board to the chassis in the order they appear on the schematic. Don't want your grounds to cross over each other.


Hate to be a PITB (that probably isn't entirely true) but if it were me I would get the solder type on/off and standby switches and scrap the snap in switch that is sitting right over that power tube socket. Those snap connections, the ribbon connections, PCB boards I would guess are made somewhere where wages are probably about $.20 per hour. They are sent to the USA where local laborers can snap an amp together in a much shorter time than it took workers in years past to make an amp. Then the manufacturer can say the amp was made in the USA. Like to see those AC wires flush with the back corner of the amp (obviously).


As a side note, purchased a rectifier tube on ebay a few weeks ago and an add popped up for 100 IN4007 diodes for $.99 (and it included shipping from China). Well I am thinking this has to be a scam but curiosity got the best of me so I bit. Regret making the purchase because I know better.


Don't have the advantage of your scientific educational background. Got my degree in business with an accounting major. One thing my education and years of international business experience has taught me is it is impossible to profit from sending 100 of anything one-half way around the world and charging $.99 for it , including shipping. Received the diodes in five or six days.


Something is seriously wrong with this. Pretty scary when you think about it. If China destroys our domestic electronics industry by pricing products below cost we will not have the electronics industry needed to defend ourselves. Well that is my preaching for the day. Just something to think about.


Thanks
Mike

[sluckey]

The way you did yours, soldered to the back of the pots, is the way Fender did their grounds historically.

I've never seen a Fender amp with a wire buss soldered to the backs of the pots.

[davegardner0]

If you look at Sluckey's picture on the last post you will notice he did his buss bar a little differently than you did. The way you did yours, soldered to the back of the pots, is the way Fender did their grounds historically. That is how I did mine on my first few builds. Potential problem with it is every pot body is a chassis ground point.


If you notice on Sluckey's picture he has a buss bar that is NOT soldered to the back of the pots. Every ground from the pot connections and the circuit board go to the buss bar. The buss board is terminated at the input jack so there is only one preamp ground connection (in your case two, one for the normal channel input jack and one for the vibrato channel input jack). Don't know that you need to redo your buss bar as Fender did it that way for a long time but information for future builds.


Remember you need to install your grounds from the circuit board to the chassis in the order they appear on the schematic. Don't want your grounds to cross over each other.

I'm curious about this single vs. multiple grounding points issue and also the grounds "crossing over"...what effect does this sort of thing have on the amp if done wrong? For instance what effect does having every pot body be a chassis ground have on the amp? Since the pot body is in contact with the chassis aren't they already grounded? I'd assume there's something subtle here I'm missing.

What about the crossing over grounds, what do you mean by that? Is that in relation to the signal chain, like the order in which the signal goes through the amp? Or do you mean the wires physically crossing each other on the board?

One other question I forgot to ask earlier, when I get to soldering the wires on the back of the turret board, should I run them in straight lines? Does it matter?

[Mike_J]

I'm curious about this single vs. multiple grounding points issue and also the grounds "crossing over"...what effect does this sort of thing have on the amp if done wrong? For instance what effect does having every pot body be a chassis ground have on the amp? Since the pot body is in contact with the chassis aren't they already grounded? I'd assume there's something subtle here I'm missing.

What about the crossing over grounds, what do you mean by that? Is that in relation to the signal chain, like the order in which the signal goes through the amp? Or do you mean the wires physically crossing each other on the board?

One other question I forgot to ask earlier, when I get to soldering the wires on the back of the turret board, should I run them in straight lines? Does it matter?

All the fuss over the grounds is to make the amp quieter and more stable. When I mention crossing over it has to do with relationship to the signal chain from input jack to output. When wiring the wires on the back of the turret board you should wire them where Doug shows them on his layout board. They are the dashed lines but you probably already knew that. Usually they are not in a straight line.


Strongly suggest that you drill a small hole next to each turret the wire terminates to or from, run the end of the wire through the hole and solder the end on the side you can see. When all of the wire is under the board the wire can fall out if it is heated by the soldering iron. If the wire falls out and you can't see it you can't tell what is keeping your amp from working properly. If you run the ends of the wires through the board and wrap it around the turret that won't happen.


Thanks
Mike

[sluckey]

I'm curious about this single vs. multiple grounding points issue

The idea is to keep power amp grounds away from preamp grounds. Power amp grounds are high current and usually kinda noisy because of less B+ filtering. Preamp grounds are low current and quiet because of much higher B+ filtering. Power amps deal with large signals, preamps deal with much smaller signals that are more susceptible to noise pickup. If you allow high current from the power tubes to flow through the same ground wire as a preamp tube, it's likely that the sensitive preamp will be affected in a noisy manner. Best to keep those grounds separated. There are plenty of successful grounding schemes out there. Many are just variations of what I just tried to explain. Amp grounding is a book of it's own. But, if you are going to use a Hoffman board, just use his grounding scheme as well. His grounding scheme is the same high quality as his boards.

what effect does having every pot body be a chassis ground have on the amp? Since the pot body is in contact with the chassis aren't they already grounded? I'd assume there's something subtle here I'm missing.

Yes, they are already grounded. It ain't about making sure the body of the pot is well grounded. It's about providing a convenient ground buss for some components (including the pot element), switches, and shielded cables, etc. Soldering the buss to the back of the pots is a personal preference. It looks neat and works well. But look at your ground buss. Looks neat but that big wire is stiff. What you gonna do if you ever need to change a pot? I bet you'll do some cussin' and start thinking of a different way to do it. That's the main reason I float my buss above the pots. A lesser reason is you need to sand the finish off the back of the pot to get a good solder connection. So, remind me again, why are you doing this? Is it just so the body of the pot will be grounded? 

when I get to soldering the wires on the back of the turret board...

They don't have to be run in straight lines but when I can, I do. I won't run a wire across a turret though. The important thing is that the wire has a reliable connection and won't fall out later when you solder something else in the turret. So, don't just poke the wire into the turret and expect it to stay there. Mike told you one good way to do it. And you can always just run the jumpers above board. I prefer that if it doesn't look too busy. Here's how I do my under board wires. Reliable and a lot less work...

[Mike_J]

The way you did yours, soldered to the back of the pots, is the way Fender did their grounds historically.

I've never seen a Fender amp with a wire buss soldered to the backs of the pots.

Fender Super Reverb (1971) and a blackface Twin Reverb I owned had the wire soldered across the back of the pots. Both purchased in the Houston area. Suppose it is possible they were serviced by a tech that liked to run a buss wire to each pot. Admit my sample would be much smaller than yours so will differ to your experience. What did they use then? That brass plate?


Thanks
Mike

[Paul1453]

I'm not sure I like your AC wiring set up.   

AC comes in, goes all the way around your output tubes and then has the fuse in between those tubes.

You have AC and your output jack very close to your PI tube.

I'm thinking that with this layout you will have 60Hz HUM and possibly other issues.   

More pictures appeared after I posted.

Sluckey's AC wiring never goes past his rectifier tube.
An expert builder's layout should be copied whenever possible.

[Mike_J]

I think you would also be better off turning the fuse assembly 180 degrees, clipping off the connectors and soldering the wires to the fuse assembly. Should be able to get the AC wires flush to the back wall of the chassis that way. You are limited by the construction of the reissue chassis. Don't know how Fender makes a stable amp with all that wiring over the power tube socket.


Look at Doug's layout document. The wires going to pin 6 of the power tubes are your power tube grid wires. The 1.5K resistors going to pin 5 of each power tube are also associated with the grid wires. You need to figure out a way to keep the AC wires away from these wires.


Run the green and black OT secondary wires straight back to the corner of the chassis and run it along the back corner to the speaker jacks. The red wire is the OT primary center tap. It is where the plates (power tube socket pins 3) get their voltage from.


See the power supply layout I created for my Deluxe Reverb build. Notice how the red wire goes to the standby switch and a red wire comes back from the standby switch next to the other wire between the rectifier and power tube sockets. At a point it goes to the positive side of the first filter cap. The red OT center tap wire also goes to the same filter cap as well as one of the black wires from the choke. Running the wire this way keeps the dirty power away from filtered power. The other black choke wire goes to the next filter which filters the screen supply (power tube pin 4). Some people like to have the positive end of the filter cap board face the power tubes. However, if you are going to place your caps near the pots then you will want your red OT CT wire and the two black choke wires coming out on the other side of the chassis similar to the where it is on the attached layout. Just requires a hole and a rubber grommet (probably another trip to Ace Hardware).


Don't pay attention to anything on the attached layout except for what I discussed.


Thanks
Mike

[Mike_J]

Attached is a picture of the way Fender wired their grounds related to pots and the circuit board. Sluckey posted these pictures a few months ago. Fender relied on the brass plate as a grounding point. Read somewhere that corrosion between the pots and brass plate has been know to cause grounding issues. Just a guess, Houston is extremely humid. Perhaps the humidity contributed to corrosion in the metal plate which is why the pots were wired together. That wire would take the place of the brass plate.


Also attached a picture of my Deluxe Reverb one-channel build. Note that all grounds go to the copper wire. Should be less of a likelihood of corrosion issues long-term with the wire versus the brass plate.


Thanks
Mike

[sluckey]

If you've never seen this, it's worth a look...

     http://deluxereverb.waynereno.com/

[davegardner0]

I bought the better quality switches, I'm hoping to put them in this weekend. I think I can orient the contacs downward in the chassis and keep all of the power wires including the unfiltered B+ in the bottom corner of the chassis.  I don't think I want to physically move the switches or fuse so hopefully this will keep things orderly and our of the way...

[Mike_J]

I bought the better quality switches, I'm hoping to put them in this weekend. I think I can orient the contacts downward in the chassis and keep all of the power wires including the unfiltered B+ in the bottom corner of the chassis.  I don't think I want to physically move the switches or fuse so hopefully this will keep things orderly and our of the way...

The Visio layout I posted above is for a Marshall style tubes up amp. In that case the contacts for the on/off and standby switches are towards the bottom of the chassis. Your chassis is tubes down. In your case the contacts should face up when you are looking in the chassis. This won''t be a problem. That will keep them even farther from the power amp tube socket. Just keep the wires flush to the back of the chassis and you should be okay.


Thanks
Mike

[eleventeen]

I don't think it's a big deal to run power by your 6V6 / 6L6 tubes. That's how (eg; where the holes for the parts are) the amp was made! It's a bit "ehhh, I dunno", but we assume the AC is twisted wires; the output tubes are swinging big volts, hundreds of time bigger than any imagined field emanating from the AC wires, and those tubes are in push-pull anyway which is inherently hum-canceling.


Too many cooks opining. It *IS* a big deal to run AC next to preamp tubes, in fact, it's potentially a big deal to run ANYTHING past preamp tubes. Or tone/vol controls.

[Mike_J]

I don't think it's a big deal to run power by your 6V6 / 6L6 tubes. That's how (eg; where the holes for the parts are) the amp was made! It's a bit "ehhh, I dunno", but we assume the AC is twisted wires; the output tubes are swinging big volts, hundreds of time bigger than any imagined field emanating from the AC wires, and those tubes are in push-pull anyway which is inherently hum-canceling.


Too many cooks opining. It *IS* a big deal to run AC next to preamp tubes, in fact, it's potentially a big deal to run ANYTHING past preamp tubes. Or tone/vol controls.

The wire going to the standby switch is unfiltered DC not twisted AC. Since he is rebuilding this amp there is no reason not to try to isolate that wire from interfering with the grid wires going to the power tubes to the extent possible. Obviously Fender constructed the amp with the standby switch sitting right on top of one of the power amp tubes. In my opinion this was much more to cut manufacturing cost versus best practices.


Don't have a degree in electrical engineering but it only seems logical that if you can isolate unfiltered DC away from a grid wire, be it preamp or power tube, you should do it. Willing to be corrected by anyone with more knowledge of the subject than myself.


Thanks
Mike

[sluckey]

The wire going to the standby switch is unfiltered DC

Not true. It is filtered by two parallel 16µF caps in the original. Ripple voltage will be under 10V. It will be fine around the power tubes.

Obviously Fender constructed the amp with the standby switch sitting right on top of one of the power amp tubes. In my opinion this was much more to cut manufacturing cost versus best practices.

How does that cut costs? Same parts count, same number of holes in the chassis, same amount of labor to mount and wire the switch.

Looking at the back of a Deluxe Reverb, I'd say the standby switch position is logical and efficient.

[Mike_J]

The wire going to the standby switch is unfiltered DC

Not true. It is filtered by two parallel 16µF caps in the original. Ripple voltage will be under 10V. It will be fine around the power tubes.

Obviously Fender constructed the amp with the standby switch sitting right on top of one of the power amp tubes. In my opinion this was much more to cut manufacturing cost versus best practices.

How does that cut costs? Same parts count, same number of holes in the chassis, same amount of labor to mount and wire the switch.

Looking at the back of a Deluxe Reverb, I'd say the standby switch position is logical and efficient.

I am confused. Looking at the Hoffman schematic and layout the standby switch is fed from pin 8 of the rectifier tube. It then feeds the first filter cap. Is this how you say it is filtered? Got the "dirty" wire idea from a post by PRR. He suggested I keep the wire away from the PI/driver. (Reply #8, Where to place the humdinger pot? thread) He said why run a sewer that way if you aren't forced to. Made good sense to me then as it does now. He still needs room for his heater wires above the sockets. Awfully crowded as it is now. Cleaning up that wiring solves the sewer issue and makes more room for heater wires. Just makes sense to me. Will differ if you still think I am off base. Looked awfully tight around that power tube socket to me.


There is a sizable labor saving in being able to snap on wires and ribbon strips instead of soldering. This is an extension of the PCB/circuit board argument in my opinion. I think the way Fender made this amp probably saves them considerable labor cost. May be the only way the amps can still be made in the USA (are they still being made here?). Get snap on parts and ribbons from somewhere in Asia and snap amps together here. I would imagine the chassis are made considerably more efficiently now then in years past with the advent of computer aided machinery but that is a side issue.


Thanks
Mike

[sluckey]

We're talking about a Fender Deluxe Reverb so I referenced the Fender schematic. Filter caps are connected directly to the rectifier tube. But it really doesn't matter if the caps are on the other side of the standby switch. When the switch is in standby mode, the amp is dead, so who cares about unfiltered B+. When in operate mode the filter caps are connected to the rectifier through the switch contacts.

IMO you're making a lot to do about nothing.

There is a sizable labor saving in being able to snap on wires and ribbon strips instead of soldering.

Now you're talking about construction techniques. Sure there's a big savings in the whole PCB technology. But I responded to your comment about the physical location of the switch.

[Mike_J]

We're talking about a Fender Deluxe Reverb so I referenced the Fender schematic. Filter caps are connected directly to the rectifier tube. But it really doesn't matter if the caps are on the other side of the standby switch. When the switch is in standby mode, the amp is dead, so who cares about unfiltered B+. When in operate mode the filter caps are connected to the rectifier through the switch contacts.

IMO you're making a lot to do about nothing.

There is a sizable labor saving in being able to snap on wires and ribbon strips instead of soldering.

Now you're talking about construction techniques. Sure there's a big savings in the whole PCB technology. But I responded to your comment about the physical location of the switch.

Thanks Sluckey, you are probably right. A lot of ways to build an amp successfully.


Thanks
Mike

[sluckey]

He said why run a sewer that way if you aren't forced to. Made good sense to me then as it does now.

And it makes good sense now. But, in that analogy, the power tubes are PART OF THE SEWER.

[davegardner0]

Finished up the shielded cable wiring:


Also wired the speaker jacks:


And the back of the turret board:


Latest iteration of the power wires...I think things are much better with the new switches.

Speaking of the new switches, I thought it was funny to find that both the old and the new are made in Mexico and there doesn't appear to be a quality difference. The new jacks take up a lot less room in the chassis, though, and the switch action feels weaker which will be easier on the fingers.

[Paul1453]

That wiring looks much better now.

The AC concern may not be an issue with your cleaned up wiring.   

[davegardner0]

when I get to soldering the wires on the back of the turret board...

They don't have to be run in straight lines but when I can, I do. I won't run a wire across a turret though. The important thing is that the wire has a reliable connection and won't fall out later when you solder something else in the turret. So, don't just poke the wire into the turret and expect it to stay there. Mike told you one good way to do it. And you can always just run the jumpers above board. I prefer that if it doesn't look too busy. Here's how I do my under board wires. Reliable and a lot less work...

I used this technique for soldering the wires to the back of the board...seemed to work well and be secure. The wires fill up most of the hole through the turret, though...what happens when the turret gets full and still needs more wires attached to it?

[sluckey]

Start by using smaller wires. Look how much room is still inside the turret in my pic. I use 22AWG and still have enough room for three more wires or three other component leads, or a mix. Four items in a turret hole is a full hole for me. But I use metal film resistors which have skinny leads. And my caps have skinny leads too. If you are using NOS CC resistors or 18AWG wire, one item is a full hole.

Look at this pic. About the center of the board you will see four resistors in one turret. They are not tight and I could force one more into that turret but that would make things difficult if you need to remove a resistor. I make four components the max on my layouts.

     http://sluckeyamps.com/6v6plexi/P-6V6_05_big.jpg

[davegardner0]

Laced up the turrets


Here's one last shot of the chassis before I install the board, in case anybody spots anything (clickable to enlarge)


It seems like a bad idea for the wires under the board to support their own weight just by the solder joints, so I added a few pieces of tape for support. I don't want them to get brittle from vibrations and break.


I wired up the first tube socket keeping the plate wires (red) away from everything else. How does this look?

[sluckey]

Very nice pics. Sharp, clear, and big.

[davegardner0]

Very nice pics. Sharp, clear, and big.

Thanks!!!

I bought a Samsung galaxy s6 a few months back...the upgrade in camera quality over my old phone (S3) is astounding! And fr what i understand its not the only newer phone with a camera this good. Highly recommended for anyone who's at least moderately into photography (like me).

[davegardner0]

Wired up the rest of the tube sockets. Feedback welcome on the lead dress. Tried to take photos at multiple angles since things are three dimensional...

V1-V3



V4-V6



V7-V8

[davegardner0]

Today I installed the filter capacitors, using the by-the-pots method. I want to keep the external bias pot from the PCB amp layout, so I had to get creative with the position of the first two caps that go to "A". I grounded the "B", "C", and "D" filter caps to the pot bus bar, but I left the "A" caps grounds unconnected for now. Those go to the chassis ground lug, right?
I also ran the wire from the standby switch, all the way around the power transformer, to "A" on the turret board.



Speaking of the grounding, I've been thinking about how that's all going to come together and I thought I'd ask for some clarification. I found this link which seems to sum up what I've been told on here about grounding: http://el34world.com/charts/grounds.htm. I have a chassis ground screw from the PCB wiring right between the turret board and the PT. I'll connect the following to it:
-the "To Power Transformer Ground Lug" callout from the bottom right of the turret board
-The ground center tap of the PT
-The grounds of the "A" filter capacitors

However the tube heaters artificial center tap appears to be already grounded on the turret board so I won't connect that. My power cord's green wire is already grounded to one of the PT mounting screws. And, the board layout doesn't show pins 1 and 8 of the power tubes grounded...is that correct or do I need to connect those?

Then for my other grounds, comparing to the link above:
-"Reverb Transformer Ground Wire" - I attached this to the sleeve terminal of the reverb/tremolo footswitch jack. (I kept the 1/4" TRS jack for the footpedal like the DRRI has)
-"Preamp Grounds" - grounded because my bus wire is connected to the back of the pots and is grounded.
-"Output Transformer Ground Wire" - currently attached to the sleeve terminals of the speaker jacks, which are not isolated from the chassis

Does this all sound right??

[eleventeen]

Looks good, in general.


I don't see a green-yel = heater CT wire, but in case I am missing it, don't have BOTH the heater CT and the artificial 2*100 ohm one. One or the other, the artificial one is actually better. It does not hurt anything to have both, just don't do it.


I like to install more than one ground lug under the PT bolt. That way you are not making a giant solder connection for your mothership ground.


Yes, [you absolutely must] ground the cathodes of the 6V6 (pin 8) unless you are going to install a bias-testpoint between those cathodes & ground by lifting them atop 1-ohm resistors.

[davegardner0]

Yes, [you absolutely must] ground the cathodes of the 6V6 (pin 8) unless you are going to install a bias-testpoint between those cathodes & ground by lifting them atop 1-ohm resistors.

So on the schematic page of the Hoffman AB763 layout I see that there's a 1 Ohm resistor between the 6V6 pin 8 and ground, and that resistor looks to be on the turret board already. So I don't need an additional wire straight to ground from pin 8, right?

[eleventeen]

Correct. Such a wire would short out that 1 ohm resistor.


Remember (or know) that a 1 ohm resistor is essentially nothing but a wire. If you have a multimeter and touch the leads together on OHMS, you'll probably get something like .2 or .4 ohms...if your meter goes that low. That's with big fat wire in the test leads, whereas in your amp, you're using probably 20 or 22 AWG = fairly thin wire = higher resistance. A 6V6 doesn't have the slightest idea what a 1 ohm resistor is. Doesn't know it's there.

[davegardner0]

Correct. Such a wire would short out that 1 ohm resistor.


Remember (or know) that a 1 ohm resistor is essentially nothing but a wire. If you have a multimeter and touch the leads together on OHMS, you'll probably get something like .2 or .4 ohms...if your meter goes that low. That's with big fat wire in the test leads, whereas in your amp, you're using probably 20 or 22 AWG = fairly thin wire = higher resistance. A 6V6 doesn't have the slightest idea what a 1 ohm resistor is. Doesn't know it's there.

Good point...I wouldn't have thought of that but it makes sense. I once replaced some 0.33 Ohm ceramic 5W resistors in a Peavey solid state amp and they measured as an open circuit if I remember.

[eleventeen]

Oh, that's a whole different story, those are "balancing"/current limiting resistors typically in the emitter legs of fat output transistors connected in parallel with each other...and often mirrored by other pairs of transistors between zero volts and the rails above and below.   


Those devices if in a typical TO-3 package are usually rated 10-15 amps; provided of course they are heat-coupled to some chunk of metal that can pull heat away from the device. In the case of your DR we're talking about output tubes that would glow bright red and possibly crack their own envelopes carrying 1/100th of that much current for any length of time! SS amps wiggle CURRENT, tube amps, volts. That's why we have say 350 volts on the plate of a 6V6 and 35-70 volts on the collector ("plate") of a 2N3055. Tubes (for the most part, in civilian applications) are high volts/low current. A speaker is powered by watts which are the product of volts * amps. Which means you can produce watts either way: Hi/lo volts---lo/high current.


 


 

[h4ck.b0x7]

I don't want to thread jack, I just thought I would put this up and ask what people think. I didn't color code the wires, I don't really care about that. I'm more concerned with comments on the AC wiring. I'm going to move the Green AC ground wire to the PT lug closest to where the AC wires come in.

Other than that I think I'm good to start putting in the board. The only things I still need to run are heater wires for the artificial CT and my wire coming from the standby switch. Any advice on running the wire from the standby switch?

[eleventeen]

Looks great! I wouldn't touch your AC line gnd, leave it where it is, it's fine.

[h4ck.b0x7]

Is it ok if the AC ground wire grounds at the same point as everything else from the power side? Main filter caps, etc.

[eleventeen]

As I recall, I think if you were to submit the thing to Underwriters Labs (UL) for their seal of approval they would want the AC gnd to have its own private screw/bolt thru the chassis but in every other respect it's fine the way it is. Looks good!

[HotBluePlates]

Today I installed the filter capacitors, using the by-the-pots method. I want to keep the external bias pot from the PCB amp layout, so I had to get creative with the position of the first two caps that go to "A". ...

To me, those two "A" node caps look scary off the board.

I'd want to see some kind of sleeving over the positive leads, or some good method of securing them which ensures the positive leads could never short to the chassis, the bias pot or a nearby bolt...

[davegardner0]

Today I installed the filter capacitors, using the by-the-pots method. I want to keep the external bias pot from the PCB amp layout, so I had to get creative with the position of the first two caps that go to "A". ...

To me, those two "A" node caps look scary off the board.

I'd want to see some kind of sleeving over the positive leads, or some good method of securing them which ensures the positive leads could never short to the chassis, the bias pot or a nearby bolt...

Should have mentioned, I glued them to the chassis (hot glue) and also used shrink tube to insulate the splice to the wire that goes to A. Do you think that's sufficient?

[HotBluePlates]

If they were mounted on a circuit board, you'd be fairly confident nothing would contact the bare positive leads. I'd almost consider electrical tape to cover those leads, and I generally have a strong distaste for electrical tape...

But I couldn't really see exactly how much room there was to the things around those caps. Either way, I'm uneasy about them.

[h4ck.b0x7]

This ought to work for the main filter caps.