VOM 8810 Project

[Platefire]

Hay Thanks PRR! I guess I was thinking the melting point was a lot lower. My new station goes from ranges from 0 to about 850 F. Most of my parts are new, so I hadn't tried to clean them  because they were new, but maybe I should?


So I never really thought about soldering temp much before  because I had no way to gauge it, but now I'm trying to catch up:>)
 
 BTW-What type and size solder do you use for general amp repair?

[PRR]

> What type and size solder

I bought pounds of 0.031" 60:40 tin:lead fluxcore in my career, RadioShack and Kester, and still have much of it.

I only had an iron with a knob on it once, and it didn't work good (it was a period with a real draft over my workbench and all my irons acted sick). The 45W dumb iron has a temperature on it but too late to look tonight. I do know it glows dim-red in dark, and easily lit cigarettes on the side.

[shooter]

because they were new, but maybe I should?

most new stuff will have a sheen of machine oil from the part making process

I bought pounds of 0.031" 60:40 tin:lead fluxcore in my career

yep, I use mostly Kester now.  working the career i'd order the good stuff 63:37 fluxcore 1 pound in the lunch pail-toolbox, couple 1 pounder's on the repair/work bench, 1 pound at home.  still got about 1/2lb roll of the 30GA for IC work.

[Platefire]

OK Thanks! I seen this at Harbor Freight when I bought my Station but I wasn't sure then but looks like it aligns with what both of you are using. I'll get it when the wife and I go shopping next week

https://www.harborfreight.com/home/hobby-tools/soldering-electrical/08mm-electrical-solder-58000.html

[WimWalther]

OK Thanks! I seen this at Harbor Freight when I bought my Station but I wasn't sure then but looks like it aligns with what both of you are using. I'll get it when the wife and I go shopping next week

https://www.harborfreight.com/home/hobby-tools/soldering-electrical/08mm-electrical-solder-58000.html

It's the correct alloy (SN63), and definitely cheap enougj, but I see no mention if it's cored or what with.

You need a rosin flux core for electronic work.

[Platefire]

Thanks,, your right. I don't see where it designates Rosin core anywhere

Looks like this link is more in order, Kester as Shooter recommend
https://www.ebay.com/itm/132402724455

[WimWalther]

If you can sneak a sample of that HF solder, melt a bit with whatever's handy - an iron, match or lighter. If it produces smoke, then it's rosin core.

Btw, $20/lb. is dirt cheap these days for SN63 electronics solder.

ETA: That listing you posted wants $11/oz. of solder.. $176/lb. ouch!

Check item #282828369148 - $40/lb and its the correct SN63 / #44 FLUX / 0.031" .material for general electronic work. Same roll that's on my bench.

Btw, solder flux does theoretically expire.. some faster than others, apparently.  But I have some 0.020" stuff from the 90s that still works just fine.. fwiw. Point is, don't worry if it's a few years out of date. Also, try to avoid "No Clean" fluxes unless you've worked with the specific material before, and are happy with its performance.

[PRR]

> Btw, $20/lb. is dirt cheap

That's a half-pound spool. $40/lb

[WimWalther]

> Btw, $20/lb. is dirt cheap

That's a half-pound spool. $40/lb

Ahhh.. good catch, 8oz. spool is right!

Well heck, just get the Kester product then.. it's guaranteed to be an excellent material. Same goes for Alphacore / Alpha Metals SN63, with a P2 flux. (Alpha P1 flux is their no-clean, same caveats apply).

[Platefire]

OK, good! It's settled, guess I'll go with the Kester. I think it said free shipping.

One more thing, what do ya'll use to clean your tip in between solder joints. On my old Weller gun, I used an old damp wash rag. On my new station, it uses a small square sponge that you dampen but seems I'm fighting to get it really clean.I also noticed that on you tube using what looks like a wad of metal material. Sometimes a small bead of solder clings to the tip and it hard to get off. Whats best?

[WimWalther]

OK, good! It's settled, guess I'll go with the Kester. I think it said free shipping.

One more thing, what do ya'll use to clean your tip in between solder joints.

An old kitchen sponge with an oblong hole cut through the middle. Keep it damp with water, distilled is ideal but straight from the tap is fine too, unless you have very hard water.

[shooter]

what do ya'll use to clean your tip in between solder joints.

I like the rear pocket from '70s era Levi's, wet, "fold" like a taco shell, lay tip between folds, pinch/wipe....quickly   

[Platefire]

Outch!  I wasn't quick enough

[WimWalther]

Btw, If you use SN62 or SN63, always keep some SN60 around to ease reworking joints, especially on P2P wiring.

Solder-suck the SN62/63 as thoroughly as possible, then reflow with SN60. Then you can rework the joint with much greater ease than if it were still made of SN62/63.

[Platefire]

Wimwalther
You lost me with those Acronyms. Don't know what you are referring to?

[shooter]

nope, but;


https://www.pcbdirectory.com/community/what-is-eutectic-solder


I called it "the perfect solder" back in my career days, mighta been just mojo like guitarist have, but I went with spending the Boss's money:)

[PRR]

> You lost me with those Acronyms.   SN62 or SN63, SN60

"SN" is Sn (from Latin stannum). You say "Tin". 62 and 63 are probably percents, but which is more Eutectic is like deciding between 3.2 and 3.3 beer. Sn60 makes radio-solder with a mild pasty phase where you can push it around. (For sculpted plumbing {and cheepness} you want a lot less Sn and plenty of Pb (Lead).)

[Platefire]

OK, Thanks for the explanation PRR. For what work we do I think you would want the solder to set up fast before something in the joint moves and degrades the joint

[WimWalther]

OK, Thanks for the explanation PRR. For what work we do I think you would want the solder to set up fast before something in the joint moves and degrades the joint

Right. You want a eutectic solder, that is, one with a very narrow (temperature wise) plastic phase. Eutectic solders go from liquid to solid almost instantaneously, with little plasticity in between. SN62 & SN63 fall into this category.

Traditional tin/lead solders alloys are designated by their tin content. SN63 is 63% tin, 37% lead. SN62 is 62% tin, 2% silver and 36% lead. This latter material is known as "silver bearing solder" and is used when soldering to precious metal plating - silver, gold, rhodium, platinum, etc. - as it prevents electrolytic leeching of these metals into the joint.

The main issue with eutectic solders is that they are much more difficult to rework compared to the common SN60/Pb40 material. This is why I suggest sucking-out & reflowing SN62/63 joints with SN60 to ease reworking.

[PRR]

....want the solder to set up fast before something in the joint moves and degrades the joint

Or set-up the joint so it won't move even without solder?

60:40 was good enough for Philco and Fender, is good enuff for me. Especially because I study my work and have been embarrassed by 'cold' joints, don't like that.

[Platefire]

24 years ago when I first started soldering guitar amps I overworked mechanical Joints where if you had to desolder and undo the joint, it was a real headache. I've now have been trying to hit a happy balance of mechanical Joints of just sound enough to make a solid solder joint and not a nightmare to tare down

[Platefire]

Got a question about installing the new CE Manufacturing Can Cap. All the previous can caps I've installed has been the clamp and bolt on like the JJ type. This one has the 4 metal tabs that fit through the 4 slots.

The old one I took off was a CE and it was installed with the tabs bent down to the chassis and soldered to chassis.Is that a proper way to do it or are they supposed to be twisted to hold them in? Or is one way is good as the other?
 

[sluckey]

In the good ole days those cans were called twist lock cans. Guess why? Even then at least one twisted tab was soldered. Fender just bent the tabs over and soldered two tabs to chassis in the Princeton Reverbs. Either way is a good electrical connection. I prefer the twist lock/solder method for a good mechanical and electrical connection.

[Platefire]

Got Ya! Thanks Sluckey

[Platefire]

Progress! Got circuit wired in. Last chore is I need to wire in AC power, power cord, fuse holder, power switch and pilot light. Not a thing of beauty being rat nest P to P but here is a few pixs

[Platefire]

Finished installing AC power hookup today and did initial fire up. Was bamboozled for a while because I was getting crazy voltage readings before I put the pre and power amp tubes in. Turns out the PT wasn't grounded. Once I took care of that the voltage reading straightened out. This is the voltage readings in general:

To PT: 371 VDC
To 6V6 Plate: 369 VDC
To 6V6 Screen 351 VDC
to 12AX7 Plates 201.7/204.2 VDC

Problem 1-At first fire up I noticed an immediate high pitched squeal. First thing I thought off was NFB, so I disconnected the NFB and the squeal quit. I'm not sure whats going on here. I know with a PP amp, you swap the plate wires from OT.On a single ended don't recall having this problem before? I changed the NFB resistor from 22K to 33K. I think because of going from 4 ohm OT to 8 ohm. I did try the NFB on the neg speaker term but didn't seem to have any effect. What do I need to do to get a working NFB loop?

Problem 2-At low volume the amp is relatively quiet but as you turn the volume up hum comes in and gets louder as you turn the volume up. I have chop sticked it a little bit but haven't really improved the situation. If the hum get louder as you turn it up, don't that mean the problem is in the power amp section???

The good news is the amp is really peppy, touch sensitive, has great tone and gets pretty loud. The tone control works really good. It comes into break up a little too quick. It really needs a good NFB loop to calm it down and give it more clean headroom. The break up sounds so good harmonically, you almost want to not complain about it. If I could get rid of the hum and get more headroom, it would be wonderful.Any help appreciated, thanks! Platefire

[shooter]

high pitched squeal

what's the bias vdc on the 6V6?

[sluckey]

Problem 1... There are probably only two wires on the OT primary, typically red and blue. Swap those two wires.

Problem 2... Probably layout. Don't I see the volume and tone controls located right above the PT? That's not ideal.

Where's the schematic???

[Platefire]

Thanks shooter and sluckey for your replys
shooter as this is cathode biased, not sure what your referring to vdc as there is no negative voltage bias circuit???
Problem 1-Got Ya! but---access is so closed in it makes it almost impossible to get access to 6V6 terms plus the blue plate lead is just a nub being the socket is so close to the OT---I would have to splice onto it for it to reach the can caps. I know making excuses don't get the job done but it's almost a sure thing that I would tear something else up trying but I'll continue looking to make a way.  See picture of access below.

Problem 2-Yelp, only 1/2" clearance between pots and transformer---see picture. Another thing I did that might be causing hum  problems where I grounded the PT. Closest available ground was an empty term on a terminal strip between the two PT secondary red leads that feed the two 500 Ohm/10W resistors that go to the rectifier. I'm thinking this might be a potential source of hum---see picture. Maybe I need to relocate this ground

Schematic: I plan to make a real schematic latter but for right now me and
Leo been using his marked up one

[shooter]

not sure what your referring to vdc

cathode VDC divided by cathode resistor IS bias voltage.
had an SE once that screamed like a PP with it leads backwards, the bias was about 2X hotter than it shoulda been. 
it's easier than hunting down inductive coupled signals in a rats nest 

[Platefire]

shooter----Cathode DC 20.92 divided by 470=.0445

[sluckey]

Problem 1-Got Ya! but---access is so closed in it makes it almost impossible to get access to 6V6 terms plus the blue plate lead is just a nub being the socket is so close to the OT---I would have to splice onto it for it to reach the can caps. I know making excuses don't get the job done but it's almost a sure thing that I would tear something else up trying but I'll continue looking to make a way.  See picture of access below.

Well then, swap the two OT secondary leads at the speaker jack. Does the same thing.

Problem 2-Yelp, only 1/2" clearance between pots and transformer---see picture. Another thing I did that might be causing hum  problems where I grounded the PT. Closest available ground was an empty term on a terminal strip between the two PT secondary red leads that feed the two 500 Ohm/10W resistors that go to the rectifier. I'm thinking this might be a potential source of hum---see picture. Maybe I need to relocate this ground

Ain't no cure for the summertime blues! Throw that crappy chassis away and rebuild in a more guitar friendly chassis. Even a shoe box is better than what you have now.   

[Platefire]

If my figures are right this amp is biased at 16.57 watts dissipation! That's about 5 watt over max
Cathode resistor measures: 476.6 OhmsVoltage drop across cathode R: 20.98 VDC
PD=(PCma)(PVv) = 20.98 Ma divided by 476.6Ohm=.044 A or 44 Ma
(PV)(.044A)=(376.7) (.044)=16.57 Watts Dis
If this is right, I am way to Hot?


 

[shooter]

EDIT ya beat me!!!

Cathode DC 20.92 divided by 470=.0445

To 6V6 Plate: 369 VDC

369-21=349
349*.0445=15.5W   i'm happy now 
so swap the speaker wires
is the speaker jack grounded to the chassis

[Platefire]

Wow Thanks! You guys did it

I swapped the speaker wires from OT  to speaker jack and hooked up the NFB wire and Wow---just what was needed. It's Fender clean up to about 12:00 on the volume. Then from there on the breakup starts kicking in with a lot of added volume. So IMHO is a good balance of clean and break up. The hum is not completely gone but is somewhat diminished to the point where I think it may be tolerable.
 
So I'm thinking if the bias is OK, we're pretty much there. I'll keep testing and see

[Platefire]

eature=shared

Sound Clip of this amp

[Platefire]

This is my first draft of the schematic with the 5F2-A married to VM 8810 transformers and rectifier. You see any mistakes,please let me know

[Calboy]

I have an 8810 as well.  I kept part of the wiring and removed other parts and built a 5f1 circuit.  Very tight space.  I did have to drill out some bigger holes and added a switch and fuse and didn't use the cap can.
I use just one input jack with a 33k resistor but there is another hole to add another input jack with 2 68k resistors for hi/low inputs.
My question is regarding the AC cord.  The original had a on/off switch connected to the volume control on top of chassis. I put a fuse and power switch at the top of chassis.
Technically, if a person does not unplug the amp if changing a tube there would be AC present nearby.  If I sold or gave away the amp how it's presently wired is this something I need to be concerned about?
Or the new owner concerned about?

[sluckey]

Technically, if a person does not unplug the amp if changing a tube there would be AC present nearby.  If I sold or gave away the amp how it's presently wired is this something I need to be concerned about?
Or the new owner concerned about?

Yes! At a minimum, put a caution sticker on the PT that basically states "SHOCK HAZARD! Unplug power cord before changing tubes."Even better to use some heat shrink tubing to insulate that fuse holder.

Or, and everyone is gonna love this... Swap the power cord white and black wires. No more shock hazard.   

[Calboy]

I like the  sticker with shock hazard which I wouldn't have thought to do.
I will do the heat shrink, I wasn't sure about what to use.
Maybe on the neutral.

[sluckey]

I like the  sticker with shock hazard which I wouldn't have thought to do.
I will do the heat shrink, I wasn't sure about what to use.
Maybe on the neutral.

Heat shrink is easy. Just get some 1" diameter tubing from electrical parts store or even Lowe's, Home Depot, etc...

[Platefire]

Just passing through to see what's going on here. Looks like all is well