1965 Deluxe tube specs

[Alexandre IV]

Hi everyone,

I just got myself a vintage 1965 blackface Deluxe (no reverb). The tubes are all different so I wonder what type of tubes should be where. From left to right, I know it's supposed to be GZ34, and then two 6V6 but then? 12at7, 12 ax7, which goes where and does what?

There is one issue with the amp, the vibrato channel has significantly lower output than the regular channel.

Anybody experiemnted with bridging the channels?

Thanks

[bob p]

check out the layout diagram at ampwares.com/ffg

[Amp Kat]

Sounds like a AA763 maybe. Cool amp. (2) 7025, 12AX7 & 12AT7. I have bridged the channels for extra gain or headroom. Schematic also at Schematic heaven

[Jag]

One of these two schematics/laytous should help you with the tube types.

AA763

AB763

12AX7 = 7025 = ECC83. Back when these amps were first built the 7025 was a tighter spec version of 12AX7. It was lower in microphonics and noise. So you can put 12AX7 in those sockets.

You can experiment with the different versions of the 12A?? tubes. The basic difference is that different models have different gain specs. For example, replacing the first 12AX7 (the one on the outside farthest from the rectifier tube) with a 12AT7, 12AY7, 12AU7, etc. will reduce the gain of the normal channel.

The weaker output on the Vibrato channel is normal to a certain degree. Whether turned on or off, the vibrato circuit loads down that channel causing the output to be weaker. It could be that there are issues there though.

In your amp, bridging the channels should work fine since both channels have the same number of gain stages. In other amps, such as the Deluxe Reverb, there is one more gain stage in the reverb channel. Since each pass through a tube inverts the signal, the two channels are out of phase, in the DR, causing the bridged tone to be weak. (A two channel amp that had two gain stages in one channel and four gain stages in the other would be fine bridged as well.)

You won't hurt anything by bridging the channels in a DR, it just won't sound very good. However, I'm sure that tone could appeal to someone.


Sorry guys, I started this reply before anyone else had responded and didn't post it until an hour later.

[Alexandre IV]

Lower output in vibrato channel

The vibrato channel is way weaker. I also have a blackfaced Deluxe reverb RI which is way louder all around. Also, the difference between the two channels is not so noticeable. I tried changing the tubes on the AB763 (dated OC for March 1965) by borrowing from my blackfaced RI but that didn't change much. I have a feeling that amp needs an inspection...

[Alexandre IV]

Ab763

Yep, it's an AB763 dated OC (march 1965).

[bob p]

The vibrato channel is way weaker. I also have a blackfaced Deluxe reverb RI which is way louder all around. Also, the difference between the two channels is not so noticeable. I tried changing the tubes on the AB763 (dated OC for March 1965) by borrowing from my blackfaced RI but that didn't change much. I have a feeling that amp needs an inspection...

if you're comfortable taking measurements, the first thing to do is to create a table that shows the voltages on the pins of all of the tubes.

[stokes]

I would suggest replacing the filter caps if you are not sure they were changed recently or are original,as well as new tubes.A NOS set of power tubes sound great in these amps,well worth the extra $$.

[Tom Phillips]

The vibrato channel is way weaker....

Try this test. Is the volume of the “Vibrato” channel affected significantly by the position of the intensity control when the tremolo is off? If so, this could be caused by continuous low resistance in the light bug.
Two reasons for the low resistance would be:
1) Bad resistive element in the light bug. They sometimes age and settle to a low resistance.
2) Problem with the light driver circuit that is keeping the neon lamp on continuously. (Note: This is a less likely scenario) Does your tremolo seem to function properly?

Another less likely problem would be a bad intensity pot. Does the pot look original? I once found that someone had changed the stock 50k pot to a 5k pot. That would cause the symptoms you are experiencing. (again not likely but a lot can happen in 42 years)

You could cut to the chase and disconnect the yellow wire from the right hand lug of the intensity pot (as viewed from the back). If your two channels then have the same gain characteristics, then you have isolated the problem to the tremolo circuit.

Anyway… don’t get too fixated on any one thing. Keep an open mind and work through the troubleshooting steps. Don’t rule out anything too quickly when dealing with your “new” 42 year old amp.

Cheers and good luck,
Tom

[Enzo]

Wow, 42 years ago. I was in college. Doesn't seem like that long.