Fender Deluxe Reverb Reissue Hoffman Board Conversion - The Basics

[h4ck.b0x7]

Does it matter that this goes to its own ground point? Considering it is over in the corner away from anything I don't think it matters.

[Willabe]

Do you think that's sufficient?

No. 

[sluckey]

The ideal ground point for that cap is the same physical point your PT red/yellow wire connects to chassis.

[davegardner0]

Do you think that's sufficient?

No. 

Hey could you elaborate some? What's the preferred filter cap mounting method? Also I should point out for clarity in the last few posts here there are photos of two different amps.

[Willabe]

Hey could you elaborate some? What's the preferred filter cap mounting method?

I would NOT trust hot glue to secure B+ filter caps to a metal chassis. ~IF~ that glue lets go........     

Would you hot glue a tube socket in place instead of bolting it to the chassis? 
 
Look at how amp companies mount there's. Fender had them soldered in place on eyelet boards for their tweed amps, later Fender used a metal 'dog house' on their black face (BF) amps to cover an eyelet board on the back side of the chassis.

Marshall and many other amp companies used filter cap cans bolted or soldered to the chassis.

All of these are solid physical connections to the amp.

Filter caps for the B+ string have hi dcv on them and the filter cap(s) for the 1st B+ power tube plate node has the highest dcv in the amp. It must be fail safe secure.

[davegardner0]

Hmmm I get what you're saying. I'll have to figure out a better way to mount them. I don't know if I can foy them anywhere else in the chassis, maybe I can figure out some sort of strap or something to mount them on right in that spot...

[eleventeen]

You could measure the diameter of those caps and get a few of those nylon "P" clamps (most often used for bundles of cable) ....Doug sells them though I don't know if he sells them with sufficient diameter...the 6th pix down on the Hoffman catalog page:

"Tube Amp Fuses, Power Cords, Fuse Holders"



Then drill a 6-32 or 8-32 clearance hole near the edge of the parts board. Place the clamp around the caps, then install the clamp "upside down" (flat side up, circular side down) with a machine screw through the parts bd and the cable clamp. Looks like you'd need this in 3 places. Definitely reco a star washer lock nut or kep nut in the picture AND a flat washer in contact with the cable clamp....I *think* you can get these at an Ace Hdwe though they are expensive there.....but those would make an excellent mechanical mounting method for them caps. 

[davegardner0]

You could measure the diameter of those caps and get a few of those nylon "P" clamps (most often used for bundles of cable) ....Doug sells them though I don't know if he sells them with sufficient diameter...the 6th pix down on the Hoffman catalog page:

"Tube Amp Fuses, Power Cords, Fuse Holders"



Then drill a 6-32 or 8-32 clearance hole near the edge of the parts board. Place the clamp around the caps, then install the clamp "upside down" (flat side up, circular side down) with a machine screw through the parts bd and the cable clamp. Looks like you'd need this in 3 places. Definitely reco a star washer lock nut or kep nut in the picture AND a flat washer in contact with the cable clamp....I *think* you can get these at an Ace Hdwe though they are expensive there.....but those would make an excellent mechanical mounting method for them caps. 

So your idea here, and any other idea I can think of, involves drilling a hole in the chassis...what's the best way to do that now that the chassis has the board, pots, wiring, etc. When I drilled the holes to mount the turret board it made a huge mess with metal shavings but I could easily clean it up and vacuum them out since the chassis was practically empty. It's a whole different situation now. But, I'm sure there's a right way to do it and not mess up the amp.
Thanks!

[eleventeen]

No, you drill these clamp-mounting holes thru the parts board which is held off the metal chassis with standoffs. Thus there is a gap under the parts board. When you drill, you have to control how much force you use so that when you break thru the parts board you don't jam the bit into the chassis---but even then, all it would do it to make an invisible gouge on the underside of the chassis. Or you could shove a scrap spoon or shim of scrap wood underneath where the drill bit would come out if you're concerned so as to protect the chassis metal. Or you can wrap a couple of inches of tape around your bit as a limiting "collar" so it will only go so far through the hole.


You get some of these type clips. https://www.securecableties.com/18-inch-uv-black-cable-clamp-100-pack


You have to size them properly for the diameter of the caps. 3/4"? 1"? Hopefully you don't have to buy 100 of them.


In every picture you'll ever see of those type of cable clamps, the flat side will be against a chassis or mounting surface and the loopy side goes around the cable bundle, up. You want to mount them upside down, flat side up and loopy side down. The clip goes around the cap and the mounting machine screw goes thru the hole you drilled in the parts board. If you are careful, you should be able to drill the hole(s), open up the cable clamp, slip it around the cap(s), and get the hardware thru the hole in the cable clamp and the parts board. A hemostat or curved needlenose is super helpful to get the hdwe aligned. You definitely want a flat washer in this picture because by the time you are using a cable clamp able to go around a 3/4" or 1" cap, the mounting hole will be too big even for 8-32.

[davegardner0]

Ok I see what you're saying now. What if i do want to drill a hole in the chassis though? I ask because I may have an alternative mounting solution with parts on hand but id need an 8-32 thru hole in the chassis.

[sluckey]

Ok I see what you're saying now. What if i do want to drill a hole in the chassis though? I ask because I may have an alternative mounting solution with parts on hand but id need an 8-32 thru hole in the chassis.

You just have to be careful and watch what you're doing. Almost every scratch build amp I do requires some drilling after a lot of wiring has been done. Same with all the conversion projects I've done.

[eleventeen]

You'll probably find that if you want to employ this scheme, you would have to drill the hole at a point that would be UNDERNEATH the parts board....necessitating its removal, and that would be a complete PITA with your wiring in place. Again, by the time you are using a cable clamp able to go around the cap, there is a significant offset between where you envision the cap [the center of the wire bundle if you were using it to hold a bundle of wires] and where the mounting screw would have to go. And people always forget to to take that into account. Or, perhaps you could drill the hole in the space between the pots, but there, one has to be careful (or countersink the screw-head) because that spot on the chassis will sit on top of the baffle board and possibly interfere with the chassis sliding in & out of the cabinet. And getting the hardware threaded onto the screw, behind the cap and at the bottom of the acute angle where the pots are would be very difficult.


Perhaps you can tell I've done this a time or two? My way is pretty simple.

[eleventeen]

Agree with Sluckey, I've never built anything that did NOT require a few holes drilled long after I thought I was all done with the mechanical part of the build. If they are small holes, 6-32 or 8-32 clearance, no big deal. If they are big holes, you just have to be careful and hope you don't mash something on the far side of the hole when the drill or reamer breaks through.

[davegardner0]

I have some of these zip tie bases
http://www.thorlabs.com/thorproduct.cfm?partnumber=CMS010
Which will hold a zip tie, and the hole would be directly under the caps. I'm thinking that will be super secure and the hole goes in an easily accessible location. Not that I don't like the P clip idea, id just rather use parts on hand.

[sluckey]

I have some of these zip tie bases
http://www.thorlabs.com/thorproduct.cfm?partnumber=CMS010
Which will hold a zip tie, and the hole would be directly under the caps. I'm thinking that will be super secure and the hole goes in an easily accessible location. Not that I don't like the P clip idea, id just rather use parts on hand.

That's perfect.

[h4ck.b0x7]

Slucky asked me to post some pictures. I can't stand the attachment size limit on here. All the pictures I take are super high quality and come out to like 4 MB each...

[h4ck.b0x7]

This is a non-empty message body, or is it?

[Paul1453]

Even though the picture size thing is a little inconvenient for users, it is a reasonable restriction.

Doug's server storage space could be eaten up quickly if we all were able to post large attachments/files.

If he could keep up with the storage demand, he would also likely incur increased bandwidth usage charges from his service provider.

I had to get used to cropping and resizing my images to post here, myself. 

[eleventeen]

Just make darn sure your mounting screws are left-hand threaded.

[sluckey]

My favorite method for mounting off board components is an insulated standoff turret. Might be something you can use too. I usually have a few in all my stuff. Look at the filter caps in this pic link...

     http://sluckeyamps.com/RCA/RCA_07.JPG

[eleventeen]

Those are great. They are also fearsome expensive to buy for some reason.

[davegardner0]

I'm just about finished populating the turret board with components. I'll of course check things a few times, but it looks like I received an extra 0.047 µF capacitor and I'm short a 1 MOhm resistor. The resistor must have fallen off of my work bench or something, but for the life of me I can't find it. Should have ordered an extra of each...

I have some 1 Meg 1/4W 5% carbon film resistors on hand, can I safely substitute one of those in? And if so, where's the best place in the circiti? I noticed the Hoffman kit came with 1/2W 1% metal film resistors throughout, is that overkill or is the 1/2W power dissipation needed? According to Ohms law for a 1 Meg resistor I'd need 500V across to dissipate 1/4W, so that does seem possible in a tube amp.

[sluckey]

I have some 1 Meg 1/4W 5% carbon film resistors on hand, can I safely substitute one of those in? And if so, where's the best place in the circiti? I noticed the Hoffman kit came with 1/2W 1% metal film resistors throughout, is that overkill or is the 1/2W power dissipation needed?

1/4W can be used in some places. My first choice would be the 1M on the input jacks, but you already have those installed. Second choice would be R59 or R60 in the tremolo oscillator circuit.

1/2 watt was a very common size back in the '50 and '60s. They may be overkill in terms of actual power dissipation in most circuits, but they usually have a sufficient voltage rating for tube use. And they are sturdier than l'il 1/4 watters. 1/4W gained popularity when low voltage transistors took over.

[sluckey]

but it looks like I received an extra 0.047 µF capacitor and I'm short a 1 MOhm resistor.

Just a crazy thought... Make sure you don't have a 1M on board in a position where a .047µF should be.   

[davegardner0]

but it looks like I received an extra 0.047 µF capacitor and I'm short a 1 MOhm resistor.

Just a crazy thought... Make sure you don't have a 1M on board in a position where a .047µF should be.   

Haha yeah I thought of that, hence the "I'll check things over a few times" plan  But, the schematic and PDF BOMs only have 3 x 0.047 uF caps and the kit page in the store has qyt = 4 so I think I'm correct there. The schematic, BOM, and web store all have 7 1 Meg resistors and I seem to only have 6 in total.

[HotBluePlates]

... I can't stand the attachment size limit on here. All the pictures I take are super high quality and come out to like 4 MB each...

There are a number of picture-hosting sites. You could also upload your pictures there (of any size you prefer) and simply post a link here...

[davegardner0]

... I can't stand the attachment size limit on here. All the pictures I take are super high quality and come out to like 4 MB each...

There are a number of picture-hosting sites. You could also upload your pictures there (of any size you prefer) and simply post a link here...

That's what I've been doing throughout, not too much effort.

[davegardner0]

I'm thinking ahead a few steps to the first power-up of the amp and I'd like to get some opinions on how to best go about it. I see on the Hoffman installation instructions (http://el34world.com/Hoffman/instructions.htm) that after checking the circuit the amp should be first powered up without tubes to check the voltages on the various tube pins. Totally makes sense to me. However the article doesn't say what voltages are acceptable for a given tube in a given amp.

What sort of voltages should I be looking for on the different tubes/pins for this particular amp?

[Paul1453]

When you power up without tubes your voltages will be high, hopefully not above your ecap's rating though.

Also without any load on the PS in many circuits you may find your B+ reading at every PS node, that is OK.

Then you want to check the pins on your sockets.
You should have your heater voltage on the corresponding pins of every socket.
Like for 6V6's pin 2 to 7 should read 6.3VAC or slightly higher unloaded.
12AX7s pins 4 to 9 and 5 to 9 should have that too.
Then the plate and screen pins on the output tubes should show your B+ referenced to ground.
The plates of your preamp tubes may also show B+ referenced to GND.
As long as you have some voltage readings on those plates they should work.
If you have a fixed bias circuit make sure you have adjustable negative voltage measured to Gnd on those pins.
Set your fixed bias reading at the high end of your - voltage range.
That should keep your output tubes from red plating at startup.

Then when you power up with the tubes in you want to see the correct voltages at each PS node.
You can then double check your preamp plates, which should now read their correct voltage referenced to ground.
Then I adjust the fixed bias voltage to the desired level.

I do those things before I try playing the amp.
Any voltage discrepancies should be addressed before you try playing. 

[davegardner0]

Then when you power up with the tubes in you want to see the correct voltages at each PS node.
You can then double check your preamp plates, which should now read their correct voltage referenced to ground.
Then I adjust the fixed bias voltage to the desired level.

Thanks for the info. By "PS node" you mean the "A", "B", "C", "D" points on the schematic? Also what would be the correct voltages on those and also on the preamp plates?

[davegardner0]

Finished the components, wired up the pots, and wired up the preamp and chassis grounds. I think all that's left are the heater wires and checking the circuit! 
(in progress)

(done)

The new cap mount worked great:

Chassis ground for the power supply and power amp:




Pots

[Willabe]

You need 1 of these, a light bulb limiter for 1st turn on, just in case there's a short.

http://sluckeyamps.com/misc/Amp_Scrapbook.pdf

[davegardner0]

Heater wires added, I think I'm pretty much done. Time to take a break and then check everything over

[eleventeen]

Well I must say, your innards look about 10x better than I imagined they would when you first started this thread. Very good!

[sluckey]

I think the footswitch jack is not wired correctly. You have the black wire from the reverb tranny connected to a hot terminal. That black wire needs to go to a ground lug on the reverb send jack. Then put a wire from the tremolo circuit to the FS jack terminal that you just removed the reverb tranny black wire from.

[davegardner0]

I think the footswitch jack is not wired correctly. You have the black wire from the reverb tranny connected to a hot terminal. That black wire needs to go to a ground lug on the reverb send jack. Then put a wire from the tremolo circuit to the FS jack terminal that you just removed the reverb tranny black wire from.

I definitely see what you're saying. Good catch!

[davegardner0]

Then when you power up with the tubes in you want to see the correct voltages at each PS node.
You can then double check your preamp plates, which should now read their correct voltage referenced to ground.
Then I adjust the fixed bias voltage to the desired level.

Thanks for the info. By "PS node" you mean the "A", "B", "C", "D" points on the schematic? Also what would be the correct voltages on those and also on the preamp plates?

Anybody have this info on the expected voltages? Can I look them up somewhere or calculate them?

[Willabe]

If the re-built amp still has the reissue PT then it should be just like the reissue.

Do a search for the Fender reissue schematic.

[h4ck.b0x7]

You need 1 of these, a light bulb limiter for 1st turn on, just in case there's a short.

http://sluckeyamps.com/misc/Amp_Scrapbook.pdf

I was just looking at this and I'm interested in building the "buckaroo". Do you or Sluckey have a recommendation for a replacement for the RS 273-1511 tranny? They don't seem to be available.

[Mike_J]

Then when you power up with the tubes in you want to see the correct voltages at each PS node.
You can then double check your preamp plates, which should now read their correct voltage referenced to ground.
Then I adjust the fixed bias voltage to the desired level.

Thanks for the info. By "PS node" you mean the "A", "B", "C", "D" points on the schematic? Also what would be the correct voltages on those and also on the preamp plates?

Anybody have this info on the expected voltages? Can I look them up somewhere or calculate them?

If you pull up the Deluxe Reverb schematic in Doug's schematic library the voltages are shown for each tube.


Thanks
Mike

[drew]

Man, these black Hoffman boards look so much better than the green snot ones.

[davegardner0]

Well after checking all of my wiring I successfully powered up the amp today! 

So far so good, it sounds really good. The tone is awesome, I forgot how much I like a blackface clean tone! And the biasing went smoothly, I was able to hit 25 mA.

The one thing that seems not quite right is the amount of hum, which is more than I expected. Especially when I turn the reverb on/up, sounds like a mains hum that comes into the signal. The amp is entirely playable and the hum is nowhere near as loud as the guitar, but still it seems a little more than it should be. What could that be caused by? If I had to guess I'd say the heater wires, I had a tough time getting them in and positioned correctly. There are wires on the tube sockets for the reverb tubes that cross over the middle of the tubes, and I have a sneaking suspicion I continued the twisted pair too close to the tubes, and thus the heater wires are close to the crossing over wires.

The other thing is that the preamp tubes are original "Fender" brand, probably came with the amp. I have no idea how old the amp is so I'm thinking new tubes are in order...

Does that sound reasonable? Anything else obvious I could check?

[sluckey]

Reverb hum seems to be a common problem in the Fender reverb circuits these days. Unplug the RCA cables that connect to the reverb tank. Still got hum with the reverb pot turned up? If so, the problem is in the reverb recovery circuit (V4). Try several different tubes. If no help, look at the grounding for the recovery stage and the RCA connectors. Some have had good luck with isolating the return jack from chassis and grounding it to the same place that V4 cathode resistors are grounded on the board. There should be a 220K resistor mounted directly on the reverb return jack. Since you used the same mounting as the original DRRI jacks, we can't see that resistor. Is it there?

Did you fix the footswitch problem? I ask because the reverb transformer secondary (black wire) was not grounded.

[davegardner0]

Reverb hum seems to be a common problem in the Fender reverb circuits these days. Unplug the RCA cables that connect to the reverb tank. Still got hum with the reverb pot turned up? If so, the problem is in the reverb recovery circuit (V4). Try several different tubes. If no help, look at the grounding for the recovery stage and the RCA connectors. Some have had good luck with isolating the return jack from chassis and grounding it to the same place that V4 cathode resistors are grounded on the board. There should be a 220K resistor mounted directly on the reverb return jack. Since you used the same mounting as the original DRRI jacks, we can't see that resistor. Is it there?

Did you fix the footswitch problem? I ask because the reverb transformer secondary (black wire) was not grounded.

Ok good thoughts I'll try out disconnecting the tank and pulling the tube. I did rewire the footswitch jack (good catch!). And I do have the 220k ground resistor, couldn't fit it on the rca return jack because of the board so I put it on the footswitch jack which is in parallel. So it's grounded to the sleeve of that TRS jack.

[Paul1453]

Nothing critically important, but I noticed on your input jack you used a red wire for the Gnd connection to the board.

I like to use red wire on wires carrying power, and black or green wires for Gnd wires.

This helps me easily identify the powered and grounded wires.   

[davegardner0]

Nothing critically important, but I noticed on your input jack you used a red wire for the Gnd connection to the board.

I like to use red wire on wires carrying power, and black or green wires for Gnd wires.

This helps me easily identify the powered and grounded wires.   

That's what I was going for but I ran out of black wire 

[Paul1453]

Depending on where the Gnd wire runs, I might even use the thick bare copper wire.   

Like on the pot lugs that connect to the Gnd bus, I tend to use the thick bare wire there.

That bare wire is also easily recognized as a Gnd wire.   

[davegardner0]

Well....I guess working on / building amps can be frustrating sometimes...

A little background: when I got this amp it had a really bad hum, which I chased all over the PCB but wasn't able to eliminate. In working on the amp the PCB started to fall apart which was my initial motivation for converting the amp to a turret board. You can read all about my failed troubleshooting here: http://www.thegearpage.net/board/index.php?threads/buzzing-fender-deluxe-reverb-reissue.1655251/

I thought in addition to vastly improving the quality of the amp, I was sure to replace whichever component was humming (since I was replacing pretty much everything).

Well, guess what the amp did the last few days when I turned it on. It started out as a hum for only a few seconds when I took the amp off standby, but now it's doing it at random, about 50% of the time.
 

On a positive note, I can count on one hand the "original" components that are still left.
-Power Transformer
-Output Transformer
-Choke
-Reverb Transformer
-Power Cord
-Pilot Light
(I could be forgetting something)

Could one of these have a ground off somewhere?? Maybe that ground tap on the power transformer? I haven't done any real troubleshooting yet (pulling tubes, etc) although I did receive the new set of tubes, which I put in and rebiased.

[Paul1453]

Random/intermittent problems are often connection issues.

Bad/cold/cool solder joints, loose wire/component, cracked or damaged component.

Problem is they are also a bitch to find.

It never seems to happen when you are in there poking around ready to find it.
But as soon as you button it back up and try to play, it's back. 

[davegardner0]

I got some "topic reply notification" emails this morning but don't see any replies since Paul's from the other day???

Either way, I'm fairly confident on my board construction/soldering/etc. and I checked the circuit after assembly. Of course there still could be a faulty connection causing intermittent ground hums. However the fact that this issue is literally exactly the same as before the amp's rebuild has me really suspicious about one of the components I didn't replace.

So what do you guys think about a ground being off in one of the transformers (maybe the PT center ground tap)? Is that something that could cause this hum? And if so, could I open up the PT and fix it or is it dead?