1965 blackface deluxe reverb

[mikep]

Hey Guys,

This is my first post so go easy! I know a little bit about testing tube amps but I'm not really great at figuring stuff out. I just picked up an all original 1965 Deluxe Reverb for a great price but site unseen. When I plugged it in it fired up but I can't get any sound. Maybe someone can figure out what I'm missing in my diagnosis.
The guitar I'm using definitely works. The guitar cable definitely works. I wanted to see
how original the amp was inside anyway so I took it out of the box. 100% original. Mallory molded coupling caps, aston cathode caps, very virgin looking. Two prong cord. Opened up the dog house, 100% original, definitely needs a cap job, some leakage. But not bad for 60 years!
O.K. so far so good. So I got my meter and started pop testing. All the plates make noise when touched with probe. There is an audible hum coming out of the test speaker. It buzzes when I touch the guitar cable.
However, no guitar sound when I plunk it.
Here are the measurements I found, which seem kinda high and maybe my problem?
Hope you guys can help.
v1-311v pin1-213v pin6
v2-312v pin1-212v pin6

v6-237v pin1-232v pin6

B+ was 436 screens were 433.
I appreciate the help,
Mike

[Enzo]

Hi

This is troubleshooting. And the essence of the process is to isolate the problem. You plug a cord into it, touch the tip of the cord, and you hear hum/noise? That tells me the amp is working. It may not work well, but it should make noise with a guitar connected. Even though this guitar works, try a different one, or a bass, or a microphone, or a tape deck, play ANYTHING through it. We want to be sure it doesn't pass signal before we go further.

If plate voltages are lower than the B+ they came from, then the tubes are conducting current. But the other half of the reading is the cathodes (pins 3 and 8) if they are zero, then the tube is not working. If they are a volt or two, that is normal. The phase inverter tube will be higher than a volt or two.

Keep your eye on the prize - the issue is no sound, not bad sound or weak sound. So the problem is not going to be an off value part or a weak tube. Leaky caps still make sound. 100k resistors that are now 200k will still make sound. "No sound" generally means some sort of gross failure. So we look for basic stuff first. And the first thing is to make sure whether the problem is really inside the amp or not.

[Chuck H]

It looks like your input tube isn't drawing current. That's most likely an open cathode circuit or failed tube. But...

I can't advocate a minimum repair to functionality for the purposes of originality because that's just not safe. You have seen leaky caps. These are failing components in a high voltage circuit without a safety ground. Nuff said IMO.

The amp should have all electrolytic caps replaced, all resistors checked for drift and, above all else, remove the death cap and install a proper three prong chassis grounded AC mains cable. If you want a museum piece you should put it behind glass and never plug it in again. If you want to play and ENJOY the amp you'll need to replace the parts that fail with age (electrolytic caps, drifted CC resistors and tubes) and upgrade the ground scheme to the modern, safe standard.

The amp is probably fine. Probably outstanding It's just old. Tubes aren't the only parts that suffer age. Originality be damned. And fire or electrocution along with it

[Enzo]

Interesting. I noted that pin 1 plate of two different tubes appeared to be high. Rather than one tube?

I agree that a lot of parts need to change, but my vote is as always to find the actual problem first, THEN proceed with updates.

[Leo_Gnardo]

Interesting. I noted that pin 1 plate of two different tubes appeared to be high. Rather than one tube?

I agree that a lot of parts need to change, but my vote is as always to find the actual problem first, THEN proceed with updates.

And in the spirit of "find the problem, fix the problem, then get on with the necessary upgrades" I'd propose there's possibly a disconnection between ground and the first preamps' cathode resistors. Check the jumper wires between that pair of 1k5 cathode resistors (paralleled with bypass caps) and the brass ground strip that runs behind all the controls.

I don't see how buzz testing the guitar cable is getting past that fault, maybe it is just producing a weak buzz. As Enzo noted, pins 3 on V1 and V2 should read 1 volt more or less.

FWIW another popular place signal goes missing in old Fenders is at the feedback node resistor. One end or the other of this (47 ohm in a Deluxe) or the wire from one end of that resistor to ground often becomes unsoldered.

mikep let's check these and get back to us. And with an ungrounded amp please don't get zapped, OK?

[pdf64]

I think that on those boards, the 0V return wire (ie from board to brass plate) for the input stages of both channels is shared; maybe that has become disconnected somehow?

[mikep]

Hey Guys,

Thanks for your replies. Here is what I did tonight with the Deluxe Reverb.
Firstly, I took all your recommendations and changed to a 3 prong cord and removed the deathcap.
Here is what I found in regards to cathode voltages.

v1-pin 3-5.24v....pin 8-1.6v
v2-pin 3-5.27v....pin 8-1.6v
v3 pin 3-7.9v
v4 pin 3-1.5v
v5 pin 3-3mv....pin 8-.92mv
v6 pin 3- 58.6v

Hopefully, this will shed some light as to the amps illness.
I went forward and ordered filter caps, cathode caps, and a bias cap.
Any and all recommendations are greatly appreciated.

[Leo_Gnardo]

Here is what I found in regards to cathode voltages.

v1-pin 3-5.24v....pin 8-1.6v
v2-pin 3-5.27v....pin 8-1.6v
....

Hopefully, this will shed some light as to the amps illness.

Yes those V1 & V2 pin 3's aren't at all what they should be. What's odd, if the jumper wire from the cathode resistors' join point to bus bar was disconnected, I expect you'd be seeing even higher cathode voltages there. In any case it's time to break out the ohm meter, and with the amp OFF measure the cathode resistors wired to V1 & V2 pin3, also measure from chassis ground to the point those two resistors join each other. The resistors should measure 1.5 kohms (a little more isn't unusual in an old amp so no panic), and chassis to the join point should be 0.0 ohms, a direct short.

[Chuck H]

Those voltages are wonky enough that I'm going to request a full voltage reading on all tubes and all pins. Remember that 4/5 and 9 on the preamp tubes and pins 2 and 7 on the power tubes should be measured for AC.

[mikep]

Wow,
Jumped out of bed to do further testing(thanks for quick response), and low and behold, the cathode ground wire to the brass
buss was disconnected. I did my best to heat the original solder with my cheap iron and was able to get it hot enough to get a somewhat suspect ground. To my great joy, when I fired the amp up and plugged my guitar in I got the luscious deluxe reverb tone I had anticipated. Absolutely amazing. Lastly, is there a trick to heating the brass buss? It seems like the heat dissipates through the bar and the solder never gets hot. Again, thanks to everyone for helping me in getting the amp up and running. I can't wait to replace the caps and cranking it!

Mike

[Chuck H]

You're just going to need to get a hotter iron. More watts can heat a space on the brass faster than it can be dissipated. That's the key. My old man had one of those industrial Weller guns with the headlamp. The lights in the house would dim when he squeezed the trigger You could hear it humming. Not kidding. He probably still has it. I have a decent solder station and I if I crank it up I can get acceptable results for small pools on a steel chassis. Fully melting large pools is out of the question. And brass is a better heat conductor so that might negate a solder station. You may need a gun.

[Leo_Gnardo]

You may need a gun.

Weller's got a big BIG pencil, 80 watts for about $30, been my go-to iron for these kind of things many years now. We've gone 'round this one before in any case. See if any of your friends have a big iron you can borrow. Anybody into making stained glass - they'll have a big iron too. Also stock up on old fashioned tin/lead 60/40 solder, Kester 44 works great for amps.

What's your location, who knows maybe one of us MEFsters can tackle that task then you can proceed on the rest yourself.

[Enzo]

I have a Weller gun, the 100/140 watt one, I have had for 60 years. That will do some chassis work like the brass plate. Anyone who has used those guns know eventually the tip breaks in half at the end - it wears away. And to get "just one more" joint, we'd bend the two halves together so they touch, and it heats again. But you can also poke the two tip ends into the work, and the current flows THROUGH the work, heating it directly. I think that is called resistance soldering. That works.