Fender Pro Reverb UltraLinear (70w)

[martin manning]

A missing ground wouldn't cause this anyway. Is your new 2k7 10W cement resistor open?

[gui_tarzan]

Nope, it measures good.

I have never seen anything like this, there are no other diodes in the circuit aside from the rectifier set and the bias. I checked with a different meter just in case, same readings. I'm going to try pulling the power section connections off and measure them separate from the rest of the circuit, adding a section back in at a time and see if I can isolate this.

It's a bugger but I will figure it out.

[martin manning]

The single connection to the part that doesn't work from the part that does is the 2k7 resistor. If you really had 800V across that it would be toast- 300mA and 240W!

[Richie]

can you post some pics of the output sockets? You replaced one? is it wired correct? Did you have these voltage readings before you replaced the socket?
What happens if you pull the output tubes, then measure the voltages? A few pics might help see whats going on.

[M Fowler]

Too bad your having so much trouble with this amp.

I recently went through one myself it had been sitting at my customer's dad's house and he finally talked his dad to let him have it. I tightened everything down first, cleaned all the pots they were terrible, replaced the screen resistors, checked the filter caps (original were fine) and retubed the power tubes/bias.

Luckily it sounded great and back to customer.

I wish the best to you to get your amp fixed.

Mark

[gui_tarzan]

Richie, I ended up replacing both power tube sockets and triple checked the wiring, even checked another version of the same schematic to make sure. The latest voltages were without any tubes in the amp. Something has to be shorted.

[67plexi]

Does this help a untouched 1978 Super Reverb.

Steve.

[Richie]

Richie, I ended up replacing both power tube sockets and triple checked the wiring, even checked another version of the same schematic to make sure. The latest voltages were without any tubes in the amp. Something has to be shorted.

I've seen people that said they checked things 100 times, but still overlook a simple miswire. That's why some good pics might help for others to look it over.
Other things that come into mind, on the filter caps, I've seen people install them and the wire under the lead can melt from the heat of the lead. It may also look fine, and not seem burned.

So you might also want to look that over. The wire from the neg voltage supply,that runs along the length of the filter section.Just throwing some things out there.

Most likely its going to be something very simple. You may just have to do as other mention, start at the power section and backtrack checking everything. from recto,filters and there connections.

[rooster]

I think your issue is filament supply oriented. You said the hum balance pot was removed? Was this replaced with two 100 ohm resistors to ground? Have you checked your AC voltage on the tube filaments?

OK, then one last thing - provided the 100 ohm resistors are installed. Have you turned the amp on in a dark room to see that EVERY tube is lit up?

[Stevem]

Rig up a way to hook up the amps speakers or any speaker to the reverb pan drive RCA Jack,
That little reverb driver transformer is a 1 watt SE amp and if the preamp section on the amp is working you will get clean sound out of the speaker!
What voltage do you read on the first two preamp tubes from pins 3 to ground and 8 to ground?
Your high 518 volts is due to some section of the amp not working and when it is not working and pulling the current it should when it's working you end up with that high B+ voltage!

[gui_tarzan]

I'll check that Steve and report back. It might not be until tomorrow night.

Thanks!

[rooster]

Too much sleep can be bad for you......

[jelle]

It is not like he is loosing sleep over it.

[Stevem]

A new Med report came out last week with new reasearch that showed that for every night that you do not get 6 to 8 hours of sleep your life will be shorter by 26 minutes!, why 26 and not 28 or a half hour leaves me wondering!

[gui_tarzan]

Sorry guys, I've been recovering from hernia surgery and I just started feeling good over the last week. I checked every connection to every part and I just don't see anything out of sorts other than a couple of resistors that have been swapped for new ones that are not the stock value, but aren't too far off.

Anyway, as far-fetched as it seemed I figured at this point it wouldn't hurt to swap the output transformer. I was thinking about this last night and since the original jacks have been changed, what if the way it was wired put too much of a load on the OT and caused an internal short? I would still get ohmage (my word), but not necessarily the correct ohmage. I didn't have a UL trans that was the right value so I put one in that is for a standard 6L6 combo and go figure, I have sound. The original OT has to be bad, like the owner suspected. Why would he suspect that? Maybe he knew something I didn't and he didn't bother to tell me? That never happens, does it?



So once again, I appreciate ALL of your help with this. I've had it way too long but health issues prevented me from getting back to it and the owner is very understanding. He's not going to like the repair cost though...