can't find: Princeton Reverb/w.tremolo test voltages info..

[TWANG]

headline says it all. I have a Fender schematic with the test voltages, but I can't find this for the Hoffman 5F2A.
thanks..

[eleventeen]

You're referring to two entirely different amps. A 5F2A "Princeton" is an early, single ended (eg; 1 qty 6V6) very simple amp that is towards the "primitive" range of things. You'll probably have to go look a Champ AA764 (single ended 6V6 w/12AX7 driver) or Vibro Champ (Doug's library) and kind of allow for the various differences for voltages; which are small. That's where I'd start. Like a 5F2A, a no-trem AA764 Champ only has a single 12A_7 and is fairly similar to a 5F2A, with a different tone control config. "Princeton" was used as a model name for this config amplifier early in Fender's history. You might also look at a Princeton 6G2....or not . 


A Princeton Reverb (AA964 or AA1164) is an entirely different animal, push-pull (dual) 6V6 output tubes, with 2 add'l 12A_7 tubes devoted to reverb and another half-tube for a trem oscillator and the other half for the PI. Because it is push-pull, it thus requires another half-tube for a phase inverter or phase splitter or "PI" as we loosely call it around here. 4 little tubes. 1 tube is preamp/tone control recovery, 1 tube is reverb driver. 1 tube is reverb recovery and wet/dry mixer. 1 tube is PI and trem oscillator. Total: 4 little tubes.


These amps are all in Doug's library.

[TWANG]

The amp is a customer build.. with a couple noises.
I got the numbers wrong for which model. My bad.
I've built quite a few amps, but never this fender type.
I just need the tube pin and other test voltages..
thanks!

[HotBluePlates]

Princeton Reverb (Schematic and layout with voltages)

Being a customer build, no guarantees they oriented the preamp tubes the same way to use certain pins on certain stages.

Voltage were +/-20% according to the schematic back then; depending on the PT used, I suspect your customer's amp will have higher voltages throughout.

[TWANG]

I have the schematic. He's done a fine job. I can't imagine anyone that neat would make the mistake of mis-orienting the tube pins. It works. the tone is pretty good.
I know, or am fairly sure, for example, that one problem was too much heat on the volume pot.. it wont work until it's about 3 or 3.5. That's very typical of a pot that caught too much heat from soldering.

I am attempting to simply find out what HOFFMANS test voltages were, and if they differ from Fender.

The oddest thing it does is squeal when any other speaker is used with it save the one he mounted in the Cabinet.
Usually that's a miswiring on the OT.. but if it really were that it should do it for any speaker.

I'll go by Fenders Princeton reverb for the time being. I just wish I had the Hoffman voltages since he was using this kit.
Thanks!

[PRR]

> squeal when any other speaker is used with it save the one he mounted in the Cabinet.

So what is so special about this speaker over "any" other?

> Usually that's a miswiring on the OT..

That's not usually a "voltages" problem.

Swapping OT leads _is_ a next step.

Alternatives are to disconnect the NFB, or use multiple external speakers parallel to see if it is critically load dependent. Maybe 4.2 Ohms lets it scream and 3.8 Ohms damps it just-enough.

[HotBluePlates]

I am attempting to simply find out what HOFFMANS test voltages were, and if they differ from Fender.
... I just wish I had the Hoffman voltages since he was using this kit.

I believe the Hoffman kit for the Princeton Reverb was a development from the Visio drawings Bnwitt did from a layout I drew up a number of years ago.

I didn't bother with voltages, because I (or Hoffman) would not have any way of knowing what power transformer got used to build the amp. In any event, normal tube troubleshooting applies: voltages within +/-20% is close enough.

There's really no use worrying unless a tube plate has something very-wrong like 40v instead of couple-hundred-volts, or a tube cathode has 50-100v when the schematic shows it should have 1-2v.

... The oddest thing it does is squeal when any other speaker is used with it save the one he mounted in the Cabinet.
Usually that's a miswiring on the OT.. but if it really were that it should do it for any speaker. ...

Unhook the wire from the speaker jack to the feedback resistor on the board. Does the squeal stop? If yes, swap the OT wires at either the primary or secondary.

Yes, it would be logical that positive feedback would squeal with all speakers, but since you just want to fix it there's not much use sorting out the why.

... one problem was too much heat on the volume pot.. it wont work until it's about 3 or 3.5. That's very typical of a pot that caught too much heat from soldering. ...

I had an original '67 Princeton Reverb, and the volume didn't come on until the volume knob was at ~2. Some pots are just like that (I could link a graph from Bourns that shows no resistance change for some rotation at both the bottom and top of the pot's range of rotation).

If it sounds good and works otherwise, I'd strongly suggest leaving the pot alone and turning it above 3. There's a good chance a replacement pot will do the exact same thing.

... He's done a fine job. I can't imagine anyone that neat would make the mistake of mis-orienting the tube pins. ...

I mean only that one could rotate the tube socket so the Fender schematic/layout shows a particular stage using pins 6, 7, 8 but the actual amp in hand is using pins 1, 2, 3. Each arrangement functions, but if you get married to pin #'s on a voltage chart it could be confusing.

[TWANG]

> squeal when any other speaker is used with it save the one he mounted in the Cabinet.

So what is so special about this speaker over "any" other?

> Usually that's a miswiring on the OT..

That's not usually a "voltages" problem.

Swapping OT leads _is_ a next step.

Alternatives are to disconnect the NFB, or use multiple external speakers parallel to see if it is critically load dependent. Maybe 4.2 Ohms lets it scream and 3.8 Ohms damps it just-enough.

I haven't checked ohms. And yes, usually it's swapping OT leads.. I wanted to have test voltages handy before I did more than I have.. pull the chassis. So each of these problems would be addressed and I'd have the voltages ready, for this amp.
NFB seems a likely candidate. He says any other speaker he has used it with. He did not put in multiple
output jacks for different ohmages. I haven't even checked his speaker, as he said 8 ohms. and my test speaker was 8 ohms.
Thanks for the NFB reminder.

[TWANG]

found the voltages page  http://el34world.com/charts/valve/ValveData.php?e=view&f=15830
just for the tubes though.

pulled the NFB off at one end... plugged my bench speaker in.. no squeal so that's that.
Assuming he likes the pretty mild increase in mid/hi tones.

the volume pot comes on at about 2 or 2.2.. no labels on this so hard to tell.. but it's starting at 1.6K roughly and goes up accordingly so I'm going to leave that.

I'm trying an AT in the Rev. though it's nice with the AU.. just to hear the difference.

The tremolo still has the flub at high intensity settings.. half way or so..
I'm going to try to reduce overall bass, slightly by changing from 25 to 4.7uF.. though I have to go check that
and see if it isn't already changed.

wish I'd not done all those marshall 18 watts sans tremolo now.. I'd know more about it!
thanks again..

[sluckey]

The tremolo still has the flub at high intensity settings.. half way or so..

That's the only downside about this type of tremolo. Change the bias setting to correct. You should be able to find a happy compromise point between your "optimum" bias setting and good tremolo operation.

Another tremolo improvement band aid is to put a diode across the outer lugs of the INTENSITY pot.

[Willabe]

pulled the NFB off at one end... plugged my bench speaker in.. no squeal so that's that.

Switch (flip/flop) the OT plate leads on the power tube sockets, then hook up the NFB, it should work now.

You were getting positive FB. There's a 50/50 chance that the OT primary wires are wrong on a new build. Many guys leave those plate wires a little long until their sure there's no problem like you were having then they go back and trim them to length.

Very common posted question/problem here. 
 

[TWANG]

Sluckey.. hey thanks I'm new to trem so that's an easy check using the bias pot.
I may be back about that diode!

Willabe.. and you, too. I'll give that a shot.

[TWANG]

bias tap and bias range are arrows pointing to the same R. using there to grnd
I get 10mV or 4.5mA on the meter.
full twist in either direction changes only 1.5mV and less in mA.

V4 trem side of tube has crazy voltages.

I forgot to test the Rect. as I was freaking on the other oddities.

All other tubes check out fine for V.
All R and continuity check out in the trem circuit.
(caps are a drag with my meter, but I'm sure they are fine.)


The Rect. does have some fairly nasty looking scratches on the top.
It's 5U4G.. I have an RCA 5U4GB that is still good, so if that's part of it, I can swap it in.

So.. I need to check the V to V4, check the Rect. Vs and figure out if I'm testing wrongly or there is something
in the B+ or whatever is going badly re: the bias test.
I may put in a new V4 just going by the idea that a bad half of that tube is causing other things.
But.. at least I'm finding out where things are off!

[sluckey]

bias tap and bias range are arrows pointing to the same R. using there to grnd
I get 10mV or 4.5mA on the meter.
full twist in either direction changes only 1.5mV and less in mA.

That's not how you adjust the bias. If this is a Hoffman board, connect your meter to one of the 6V6 sockets, pin 8. Adjust the bias for 25mVDC on pin 8. This is just a preliminary bias setting but it should allow the tremolo to work.

V4 trem side of tube has crazy voltages.

Yes, that means the trem oscillator is working.

I forgot to test the Rect. as I was freaking on the other oddities.

Your rectifier is fine.

[TWANG]

bias tap and bias range are arrows pointing to the same R. using there to grnd
I get 10mV or 4.5mA on the meter.
full twist in either direction changes only 1.5mV and less in mA.

That's not how you adjust the bias. If this is a Hoffman board, connect your meter to one of the 6V6 sockets, pin 8. Adjust the bias for 25mVDC on pin 8. This is just a preliminary bias setting but it should allow the tremolo to work.

I've only done one of these.. a pv classic 30.. and the setup I put in was wired differently.
It's been two years since I got sick and I'm not surprised at how doofus I am about it at all.
Sorry to bug you guys with that, though.

I have been reading around.. I did see some saying the fenders could be biased lower.. but since it's hoffman
I'll try your numbers.
One site said the trem might have that flub, when the intensity is high, disappear IF you go as low as 20mVDC.
I can adjust that easily enough.

V4 trem side of tube has crazy voltages.

Yes, that means the trem oscillator is working.

Oh, good. You can see where I thought the tube might be bad. 1,3, 6, 7, 8:  351, .1, 172, 17, 47.3

I forgot to test the Rect. as I was freaking on the other oddities.

Your rectifier is fine.

It does have goofy voltages though. 2, 4, 6, 8: 373   9.8  8.9  372
B+reads ok.
I'll rebias according to the above. See what's shakin'!
I get 29 and 30 on pin 8 of V5/6 currently. so, again, that could be the trem problem re: the flub.

[sluckey]

It does have goofy voltages though. 2, 4, 6, 8: 373   9.8  8.9  372

Those voltages are fine. You have to turn a knob on your meter when reading the voltages on pins 4 and 6 because they are AC, not DC.

Diddle with the bias pot while playing the amp. Set it to a point where you like the sound of the amp and have good tremolo, ***AND*** the 6V6s are not turning red inside. I bet you will be close to 25mV in pin 8. If not, be happy. Don't worry.

[TWANG]

my meter is auto ranging so no knobs to twist.
I'll check it though.. set it and put the leads over a 9V battery.

I have the bias at 21.8mVDC.
It was set at 55!

still no tremolo at all.
everything else works fine.

[sluckey]

my meter is auto ranging so no knobs to twist.

Auto ranging is not the same as switching from AC function to DC function. Surely you have to push a button or twist or flip something to change from measuring dc volts to measuring ac volts. What meter do you have?

[TWANG]

It just changes from V to mV. put on a 9VDC battery, it reads 9V.

anyway.. I think I have it.

First I switched the Rect tube to my RCA.
It gives slightly higher voltages than what was in it. But consistent throughout.

also, it gives slightly higher V for pins 4/6. up from 9.8 to 13.2 on each pin.

V4A shows a raise, as well.
going P1, 3. 6, 7, 8, first tube/JAN replacement tube:
I read 351/375
.1/.1
172/182
17/18.4
47.3/51

So I looked at the sche/layout again..
P6V3B has a wire under the board, which runs to P7V4B.
I test with ohms and get OL.
That seems to be odd, however, to me at least, since that's signal, and that side of the tube seems
to be being fed.

Tests on V4A certainly indicate consistent V's that are way high, and too low. on P1/3.

So, I have straight under board wire that resists Ohms readings coming from the Preamp
to V4B although the  tube tests V's correctly.

I have run as many checks on the R's and all turrets connect points possible, and there are
correct results.
I have switched V4 out and gotten quite similar results with both tubes.
Same with Rect.

Yet, no tremolo.

I can't hurt anything by sneaking a straight wire, replacing the under board wire I tested negative
above. Should give me an Ohms and continuity reading.
If that does as I think, then I could hook it up temporarily w. solder and check V's again.

I'm also, first, in fact, going to double check the control pots to circuit.
Though I don't find any explanation there, or in replacing the wire, for the odd V's.

Probably right under my nose.. and I'm just not thinking right.

[sluckey]

So I looked at the sche/layout again..
P6V3B has a wire under the board, which runs to P7V4B.

No it does not. Look again, more closely.

[PRR]

> It just changes from V to mV. put on a 9VDC battery, it reads 9V.

Meters do not "auto" from AC to DC. (Unless they have multiple displays.)

Put the meter on _AC_. Measure a 9V battery. It reads "zero". There is no AC out of a battery. On DC it reads the 9V.

Put the meter on _DC_. Measure a 6V heater winding (end to end, not to ground). It reads "zero". There is no DC in a heater winding. On AC it measures the 6V.

In these cases, the meter "could" guess which reading you want, by checking both and showing the larger one. However there are many cases where there is both AC and DC across two points. And you may actually need to know either mode. I have never seen a single-display meter which tried to be that smart; I would hate it if it did.

[TWANG]

yep. blue button. I could have sworn it changed auto. My bad.
4/6 331 each. Just fine.

there's a dotted line on the layout, and another on the board for grounds.
I assumed it was another line underneath.

still no tremolo.
I went through every bit of the trem circuit.
All I can find is .. no trem. and pins 1/3 of V4A.
I can't find a thing wrong otherwise.
Are there ways to test any volt or signal while
it's live?

I probably could find another solder joint to mess with, but
they all check out so.. seems very unlikely.

[sluckey]

I suppose I misinterpreted this statement...
 

The tremolo still has the flub at high intensity settings.. half way or so..

I took that to mean that tremolo works but it gets flubby acting at high intensity. Is my interpretation wrong?  Do you really have absolutely no tremolo effect at all?

V4 trem side of tube has crazy voltages.

Again, those crazy voltages means the tremolo tube V4 is working properly. If you want to see some steady state voltages on that tube you need to turn off the tremolo by using the footswitch or by putting a jumper clip lead between the tip of the footswitch and chassis. Once the trem is turned off the voltages will be steady and you can compare them to the voltages on the schematic. As soon as you turn the trem back on V4 voltages will start changing at the speed of the tremolo oscillator. This will just appear as crazy random voltages to a digital meter.

So, based on what you have told us the trem oscillator V4 is working, but the trem signal is not getting to the Intensity pot. The only thing between V4 pin 1 and the INT pot is R63, C30, and C31, and a wire. (Look at the Hoffman schematic.)

If you still can't find the error, post some hi rez pics that show V4 socket, the INT pot, wiring, and the part of the board that holds the components that I mentioned above.

[TWANG]

Yeah, no trem at all.
Oddly, nothing was touched except one cap in the preamp. It just stopped.
I first went with reflow. and some r tests, then got serious about all of both.
I even tried to put a FS on it just to see if turning it on or off would make a difference.

I'll put the FS back in and test V's that way. Thanks for that, I wouldn't have thought of it.

I've been over the path you posted from INT. But I'll do it again.
I traced every possible path out to V3 and V4 and got good tests.
I think, it's those turrets. they are sort of tiny inside and it could be there's
a cold solder sort of hidden in there, depending on what is connected where, maybe..
I'll see.

[sluckey]

Yeah, no trem at all. Oddly, nothing was touched except one cap in the preamp. It just stopped.

This sounds like you had tremolo at one point and then it quit? Is that true?

If that's the case look to what you have done either directly or inadvertently without knowing. And of course it could be that it just quit coincidentally.

Either way, since the oscillator seems to be working, there's not much more that could be a problem.

If you really suspect a turret just reheat and feed a little bit more solder into it. Just don't overdo it and create a blob hanging out the bottom of the turret.
 

[TWANG]

Yeah it worked fine except for some oddness when the INT was 1/2 way or higher.
I changed a single cap, off the input to V1 from.022 to 4.7uF.
It's fine there and shouldn't have had any effect on the trem save to reduce the lows a bit or tighten
them up.

It is the only thing I touched prior to losing the tremolo.
I'll reflow.
I checked for R and C. they all read fine.. wire, too. Pot works fine.
(going from the points you mentioned)

Of course I did reflow some solder but that was after I lost the trem.
Back I go!
and thanks again.

[TWANG]

5. Tremolo doesn't work
Replace the fifth tube from the right (forth on a Princeton, second on a Vibro-Champ, third on a non reverb amp) looking from the back (12AX7). If that doesn't do it you should check to make sure that your footswitch is working properly. The tremolo will not work on blackface/silverface Fenders without the footswitches plugged in on almost all the amps.
No Vibrato

Vibrato tube going bad, either the oscillator section or the driver section; swap it and see.
Neon/LDR module going bad (Some Fenders)
Broken/open resistor, capacitor, or wiring
Faulty speed or intensity control
Faulty vibrato footswitch , jack, or wiring

These pages aren't much help.
First, he has a stereo jack in the Trem FS.. but, the tremolo worked with no FS connected when he brought it over.
I can change that, no problem.
So that leaves me with wiring..the parts all check on the meter, so does the pathway. the pots test correctly.

It's maddening.

[HotBluePlates]

At this point, it would probably be best if you post/link some high-res photos of the chassis, so we can see what's going on.

[TWANG]

OK but really, you're not going to see anything, I'd bet, anyway.
It's like this with only some of the tube sockets turned a bit.

http://el34world.com/Hoffman/files/Hoffman_PrincetonReverb.pdf

I'll get the camera out there.
Ok.. here we go.
http://i.imgur.com/YPgIniW.jpg

this should be the entire album..
http://imgur.com/a/InxEP

[HotBluePlates]

Okay, so what exactly doesn't work?

I ask because when this thread started, we were only concerned with squealing & a volume control which seemed to kick on volume slowly. Those are now resolved/dismissed, and the trem which seemed operational before is now not working? No pulsing sound at all?

[sluckey]

That board looks like it has acid core solder on it. Does it?

[TWANG]

It squealed with any speaker but the one it came with.
so I pulled the NFB and that stopped.

the volume control seemed to not work until it was fairly high, but it's really fine.
just has to be about 2 and it goes up gradually so.. works well.

the trem simply stopped! It worked, he played his steel through it, I really liked it quite a bit.
next time I plugged it in. zip. no pulsing nothing.

I did not ask him about the solder, I will. Yes I noticed it myself. the grayish and kind of dirty look.
I did mention to him, last night, that I use silver solder.. but he didn't bring it up.
I should say.. the amp works fine in all respects save the trem, so it didn't seem to me that solder
would be the prob.

[sluckey]

I highly recommend you use 60/40 lead/tin solder. Your silver solder will not mix well. Look at the 4.7µF cap you put in.

Acid core solder will result in some bad solder connections that may cause intermittent problems, such as trem that worked fine until you started moving things. And the acid will eventually cause big time problems.

Post the voltages for V4 pins 1, 2, and 3 again please.

[HotBluePlates]

I would simply measure for a.c. volts at the junction of the 220kΩ resistors (R47, R48 where the wire runs to the Intensity pot) which go to the output tube pins.

You don't have the tremolo footswitch plugged into the amp do you? And no tinkering with that jack?

[TWANG]

We're on to something for sure.
V4A 1 2 3
369   .8   1.1

R47/R48 junction... -33.5mV   VAC jumps around

So there's a problem with the solder there.. though they were reflowed.
I always us a tick of solder, because it help heat the cold solder faster.

But it appears it doesn't mix well. argh! I should have asked him about what solder he used.

[HotBluePlates]

R47/R48 junction... -33.5mV   VAC jumps around ...

Are you sure this is millivolts a.c.? Because -33.5 volts d.c. would be very believable as your bias voltage at that point. And because the a.c. tremolo voltage is superimposed on this, if you measure d.c. volts with a digital multimeter, the reading would bobble around.

However, if you were measuring a.c. volts, you would almost certainly not see a negative number and it would likely be 20-30 vac and quite steady (unless you're adjusting the Intensity control).

What is the make/model of your meter?

[TWANG]

Tenma 72-7735 about 7/8 years old.

I set it V AC   it jumps around.
I hit the button for mV and it gives -33.3, but shows V on the screen instead of mV.
(but the AC is also no longer on the screen, so as previously I assume it's VDC)

Clearly though, it varies as to where you put the probe.. now and then holding it firm
it hit 0.L
Sometimes it hits 0.00 but only on AC.

I think I need to re-solder that junction for sure, because it shouldn't be that funky.

And it's started to make a slight crackle, volume down, when I'm testing.

[Cobbler]

FYI...I built the amp in question and brought it to Twang for some help on the speaker issue.

The solder used was Oatey 40/tin -60/lead rosin core.

[HotBluePlates]

Tenma 72-7735 about 7/8 years old.

I set it V AC   it jumps around.
I hit the button for mV and it gives -33.3, but shows V on the screen instead of mV.
(but the AC is also no longer on the screen, so as previously I assume it's VDC) ...

Gotcha. From the manual, you'll be hitting the blue button to toggle from DC to AC voltage measurement. The -33.3v is then likely while in DC mode, so keep autoranging on and switch over to AC.

The point at R47 & R48 should also have a wire back to the middle lug of the Intensity pot. If you get 0v AC at R47 & R48, you should then make the same measurement at the Intensity pot's middle lug to verify the wire is okay.

No AC volts at the middle lug? Move to measuring AC volts at the right lug, as seen from the back of the pot (this is the side that connects to the oscillator circuit output).

Keep walking the circuit back from the 220kΩ resistors to the oscillator to find where the AC volts starts/stops. Earlier, you were getting likely AC volts at the plate of the oscillator tube, so probably the tube stage is working correctly. So you'll have to hunt for where/why the trem voltage stops being relayed out to the output tube grids.

[TWANG]

had to food.
then
DER KOMMANDANT
issued orders.

I started right at V4P6 where it meets R47.
AC.. 0.00 V.
the other side of R47 the meter jumps all over.
and, continues to jump to the pot and beyond.

So 1W 220K R will go in first. And hopefully, that's the only place.
But.. now I have a really good method beyond testing components wires etc.

Cool beans. I finally feel halfway decent about this.
thanks very much!

more later, .. if that IS my real name.

[sluckey]

I started right at V4P6 where it meets R47.

V4P6 does not meet R47. V4P6 also has nothing to do with the tremolo.

[TWANG]

sorry did by memory.
V5P6 meets at R47.
The other side of R47 runs to the Intensity pot.
But the other voltages, to the R. are normal.
Where through that R47 they are not.

So the Intensity pot middle lug is not getting what Vs it should recieve due to R47
not working.
Does that not explain the trem loss?
 

[TWANG]

Ok.
V5 P6 to R47, R48, to Middle lug INT pot, to C30
-32mV all the way.

I replaced R47.

C30 on the other side gets 340V.

So it seems to me the inconsistencies I had were fixed by replace R47. Now those V's
all check right through the pot.

But at C30, Which eventually reaches V4 P1 has about the same V as the pin.
I guess that I need to replace C30 with a new .1uF.

[HotBluePlates]

Ok.
V5 P6 to R47, R48, to Middle lug INT pot, to C30
-32mV all the way.

I replaced R47.

C30 on the other side gets 340V. ...

   You're still measuring d.c. volts, and a.c. tremolo voltage is all that matters at this point. 

I'm out... I just can't hang anymore.   

[TWANG]

Here's what I did.
it wouldn't read ACV at R47/48
it would read mV.
but it was not consistent at R47 so I replaced it.
Consistency being all I had to go on since the ACV jumped all over.
Now, it reads the same thing all the way back.

Back meaning, to P1V4A.

the odd things:

I can test ACV at V4P1 and get 28V.
I get that at the first junction of cap and R. But not
beyond.
After R63 it starts jumping again.

So my mV test ran me to C30..
 BUT
if I test to where it jumps
and then go back.. even V4P1 wont give me ACV again.
For some reason I have to wait 30 seconds.. and then it reads ACV again.
Sooo.. I have looked at what is inconsistent..I wasn't not following your directions.
I was only doing what the circuit would let me.

Is it my meter? Bad battery? (regarding the will test wont test problem.)

Is it R63, or C30? Or a bad solder joint junction of C22 and R63?
It's apparently right there since the mV led to there.. just as if I'd used ACV and gotten
the jumpy readings would have led me there.
(by the way.. I did.. it was consistently jumpy with ACV after I replaced R47. again bad R or solder joint fixed)

IOW I did follow your instructions I just ad libbed a bit using what readings I could get.
so again V4P1 28VAC junction of C22 and R63 also.
Beyond that, jumpy.

EDIT
reflowed solder at junction of cap and R off P1V4A
26 VAC at pin, to junction, through R, drops to 21.6VAC after that R..
next cap reads same..
other side of that cap reads 0V.
It's a new cap!
It can't be stopping V through the cap.
So it has to be either a solder drip to chassis under the board.
or the solder joint connecting the wire to the right lug INT pot sucks.

Either way, mV or VAC we find our way to C30 point where things are stopping.
I'll let it cool and see if I can make that solder joint work.

[Willabe]

These are the 4 points you need to measure for ACV's on auto range.

[TWANG]

Yes point one on your diagram read 21VAC
meter on AC, Auto.
point three fails to read V. all points beyond that, at the pot and through the pot also fail.
It keeps coming back to C30.
Point four on the diagram also wont read V. Only mV.

[HotBluePlates]

Twang, I promise I'm saying this while intending complete respect.

I don't trust any of your voltage measurements because when asked for a.c. voltage measurements, you keep giving ones which are obviously d.c. And your meter requires you to press the blue button to toggle between d.c. and a.c. volts modes, and I think you keep overlooking that while thinking the auto-ranging will do the switching for you.

Because I can't have faith in the numbers you provide being what is asked for, that's why I'm bowing out of this thread. I hope you get the amp sorted out. Perhaps using your friend's meter instead of that Tenma will be helpful.

[TWANG]

Twang, I promise I'm saying this while intending complete respect.

I don't trust any of your voltage measurements because when asked for a.c. voltage measurements, you keep giving ones which are obviously d.c. And your meter requires you to press the blue button to toggle between d.c. and a.c. volts modes, and I think you keep overlooking that while thinking the auto-ranging will do the switching for you.

Because I can't have faith in the numbers you provide being what is asked for, that's why I'm bowing out of this thread. I hope you get the amp sorted out. Perhaps using your friend's meter instead of that Tenma will be helpful.

Actually, you're a little bit wrong.
I do set the meter for AC and test. It jumped all over.
But the mV gave consistent readings except for R47, which I switched out, and then they were consistent.
I used those to C30 where they changed on the other side again.
Then I did what you said.. ACV from V4P1 to C30.. until I got to the far side.. where all the ACVs were jumpy.
I know I didn't say that very well, and I'm not angry or anything about you losing interest.
But I really was doing both things.

As of now, I reflowed C30 and I'm still not getting the 21VAC that's on the other side of it.
I have to try that again. maybe there's a solder drip.
maybe I just failed to reflow well enough.
I have some better wire, maybe that's it.
But it does seem that C30's pot lug side solder joint is not getting the V's from it's other side.
I'm assuming that it doesn't drop, but even if it's supposed to, the meter just jumps around and wont settle
to an VAC.

On the bright side, I got my Tweed 5D3 working again.. bad rectifier tube.

[tubeswell]

You may have a dud meter.


On the question of the cap you 'replaced' before the trem quit working, it's usually the case that if you did some modification and something stopped working, its probably because of the modification you did. In this case, either putting in a bad cap, or bad soldering. (Maybe one of the cap leads is shorting to the chassis?) Build pictures would help.