5Y3 in a Princeton Reverb?

[Jasonpatrick]

Hey just for laughs, unscrew the screw completely out that’s holding the board down next to the 1k. Getting continuity still?

 

[Jasonpatrick]

Also, if you unhook the wire going to point B at pin 4 on the power tube, still getting continuity?

 

[peteb]

Can anyone verify if the red wire off the reverb transformer should or should not show continuity to ground?
Both the green wire and the red wire show continuity to ground and of course all the "B" nodes on the layout which are circled.. (no switch or reverb cables plugged in)

I am not familiar with reverb circuitry.

It looks like node B connects to the Primary of the reverb transformer and should not have continuity to ground.

The secondary connects to ground and would therefore have continuity to ground.

Any continuity between the primary and the secondary?

 

[2L man]

Can anyone verify if the red wire off the reverb transformer should or should not show continuity to ground?
Both the green wire and the red wire show continuity to ground and of course all the "B" nodes on the layout which are circled..

Not! Primary should show infinite resistance to its iron and secondary or at least megaohms. You found the Short!!!

 

[schmee]

Also, if you unhook the wire going to point B at pin 4 on the power tube, still getting continuity?

Yes still get continuity with it disconnected.

I am not familiar with reverb circuitry.

It looks like node B connects to the Primary of the reverb transformer and should not have continuity to ground.

The secondary connects to ground and would therefore have continuity to ground.

Any continuity between the primary and the secondary?

Disconnecting the Red reverb wire from the circuit results in a change to no continuity to ground from any of the B labeled points. I think that verifies the reverb tranny went bad. It was still working until I took it out of the amp!

There is NO continuity from the Red wire to the Blue wire on the tube socket.
There IS continuity from the Red wire to the Green wire on the RCA jack.

 

[Jasonpatrick]

Yes still get continuity with it disconnected.

Disconnecting the Red reverb wire from the circuit results in a change to no continuity to ground from any of the B labeled points. I think that verifies the reverb tranny went bad. It was still working until I took it out of the amp!

There is NO continuity from the Red wire to the Blue wire on the tube socket.
There IS continuity from the Red wire to the Green wire on the RCA jack.

I once hastily installed a reverb trans and one of the strands of braided wire didn’t make it through the hole and ended up making contact with the heaters, transformer got super hot and leaked some of its wax out haha, but still worked after the fact

 

[schmee]

Update: Well the Reverb tranny came and that fixed the issue!
I havent played it yet other than to test out of the cabinet. But it's all biased and ready.

That's life working on amps I guess, athe amp was working when taken from the cab, on the test bed it starts smoking. Sure enough the Reverb Tranny is shorted. Go figure, Maybe not having a tank connected was the last straw! Although I have played some amps for a very long time with no tank in the past.

I put a 5V4 rectifier in. Was going to try a 5R4 as @Wally suggested, but lo and behold I have no 5R4s! I have no idea where they went as I can't think of an amp I have actually left one in, but know I had a couple around..? But I'm old and forget things!

 

[NTC]

That's life working on amps I guess, athe amp was working when taken from the cab, on the test bed it starts smoking. Sure enough the Reverb Tranny is shorted. Go figure, Maybe not having a tank connected was the last straw!

That is analogous to playing the amp with no speaker. The power has to go somewhere.

 

[schmee]

That is analogous to playing the amp with no speaker. The power has to go somewhere.

Yes, in theory that is correct. Strangely it's never been an issue for me.

This story might have people who work on amps thinking they need to connect a tank when they have the chassis on the bench!
I wonder... HOW MANY OF YOU OUT THERE DO THAT?
It also makes me wonder if the "nasty" I was experiencing, which is why I took the chassis out, was caused by the that "ready to blow" Reverb tranny?

 

[David S]

I almost always keep a tank connected. Years ago I had a client with a tank that had one broken spring. I kept that tank. It has a six foot cable hooked up as well as female-female RCA adaptors. Very handy for testing. Sits on a shelf near my bench

 

[schmee]

I almost always keep a tank connected. Years ago I had a client with a tank that had one broken spring. I kept that tank. It has a six foot cable hooked up as well as female-female RCA adaptors. Very handy for testing. Sits on a shelf near my bench

I wonder how big a resistor it would take to rig up a little "RCA jack plug-in resistance" for this type of thing...?

 

[schmee]

The amp is working, it hums more than it used to from 1-3 , quiet at 4 ish, then hums at 5 and up.
I need to try it out of this room and see if it changes.

 

[schmee]

OK, the amp sounds good at volume. I have one issue though:

The amp hums, it used to be my quietest amp. It's not a harsh AC hum, but more subdued however still too much to be normal. It hums in the cabinet or out.
-At 4 on the volume it's quiet. Going either way up or down produces hum. (At 3 on the volume it hums and hums from 3 to 0 also. It hums at 5 on up also.)
-Not reverb related: The hum does not go away with the reverb tank disconnected or the reverb send tube (V2) pulled.
-I tried different pre tube, PI tube, power tubes and rectifier tube with no change.
-I looked for solder flows that were messy and resoldered.
-I changed out the volume pot.
-I tried different house locations.
No change.

I'll get voltages today, but anything jump to mind with a volume pot creating hum everywhere but at 4?