The Amp Garage

I don’t know if it’s been mentioned in this string since I am not reading through it all, but I am firmly of the opinion that how components are mounted next to each other will have the most effect on sound / tone . Performeance. Especially the installation of coupling caps In the way that bleeds th...

In terms of the whole amp then look at a Fender deluxe reverb.

That amp has more tubes and more wattage then the Vox and is powered on only a 1 amp SB fuse.

If you disconnect everything from pin 5 on each output and remove both output tubes do you see any residual dc or ac vintage there ? How about with the tubes in the socket’s and just direct bias voltage fed to pins 5? On the PI tube side of things is there any Stray Dc voltage on the grid with the t...

Are you talking about the total ma load, or just the output section?

I was going by the RCA tube manual that called out 92 ma , 300 B+, 17 watts.

Get in touch with the local Ham radio community near you. 75% of those folks have good tube testers that can test for the Gm factor which is really what you want to know if the tube is not just a simple rectifier. You would also be then likely to find a member who might buy a lot of those tubes from...

I can’t see for the life of me why the whole amp, as in the AC-15 schematic would need anything more then a 1 amp slow blow fuse. What I would do is add a 100 ma fuse into the OT center tap. When the main AC fuse blows in a amp 99% of the time it’s due to a shorted output tube and EL84s it seems lov...

Yes that thread explains what to do. To test out individual gain stages for hiss you can jump out the plate load resistor and that will kill all the gain. Also sometimes what people call hiss is 120 hz buzz. If you have no metal plate covering the open side of the chassis when in the cabinet or when...

When you have no cable in a input jack it is shorted and the first gain stage is not functioning from the grid back to the jack. I would then suspect a bad noisy resistor, either on the input jack or the ground reference which is usual a high value like a 1 meg. And yes even new resistors can be qui...

Sounds to me like one side of the primary of the amps OT has a issue if indeed there is no coupling cap leaking D.C to that tube sockets grid. Unsolder the 3 wires on its primary side and and use a AC wall wart to perform a OT check that you can find on line. Make sure that the speaker output jack i...

Please note that if you keep on blowing fuses of the correct 1 amp slow blow type there’s a real good chance of shorting out the power transformer.

These can only take do much before going south!

You have to narrow it down to a wiring issue or a tube issue. Pull out the output tubes replace the fuse and plug it in direct , does the fuse then blow? That amp takes a 1 amp slow blow fuse, is that what you have in it? Another thing you can do to narrow things down is to yank out all the tubes. I...

I have fixed a few output transformers where the feed wires out of core broke there connection to the winding. The question always comes down to how deep in the winding core did the feed wire go to make its connection to the actual winding. I use a Xacto knife to cut into and then un-rap the paper a...

One main thing to start with is with the secondary center tap off the PT. This ground wire needs to right to the first power supply filter and then a wire is run from there to a post on the chassis where all other combined main grounds go to. Meaning like all the combined grounds from the preamp sec...

Needing them at in terms of a push pull class A amp can depend on your plate voltage. Once you get close to 300 on the plates it’s good to have a 100 ohm resistor on each off of the B+ feed to them. You don’t want the screens sitting at the same voltage as the plates . 99% of the time when a power t...

Opp’s!