Early 60's Ampeg Reverberocket: need help with noise

[Jonny toetags]

So I have this old Ampeg Reverberocket 1x12 combo that has some issues.
I've fixed a few of them and the last (but biggest) is the noise issue.
How would you go about diagnosing this circuit? It's really tight in there!

[Mick Bailey]

What kind of noise - hum/buzz, hiss, random disturbance? The type of noise can act as a pointer.
Do any of the controls affect it?

[cyclone]

pink caps, get rid of them

I went through one of those recently, every single one of those pink caps was leakier than a screen door. I tested every single caps insulation resistance with my TO5 Sprague, only the pink ones were bad.

[Jonny toetags]

I went through one of those recently, every single one of those pink caps was leakier than a screen door. I tested every single caps insulation resistance with my TO5 Sprague, only the pink ones were bad. [ATTACH=CONFIG]27138[/ATTACH]

What did you replace them with?

[Jonny toetags]

Sorry, been away since I started this thread.

So I go to turn on the amp to figure out if it is more of a hiss or hum..and now there is no sound.

[Jonny toetags]

The noise is a hum.
With no guitar plugged in, the hum is there. If as I crank the volume, the hum does not get any louder. I can hear the usual hiss from a cranked amp slowly appear, but the hum stays the same at 0 or volume at 10.
I'm going to switch out the 3 pinkish caps mentioned by cyclone and take it from there.

[Jazz P Bass]

What you should do is find the source of the hum.

The first place to 'look' is the electrolytic capacitors.

Make a connection with your voltmeter on the cap in question.
Measure the volts dc & then flip your meter to read volts ac.
A high Vac reading (ripple) indicates a bad cap.
By placing a known good cap of the same value & voltage across the cap, if the ripple lowers, that cap is most probably bad.

[soundguruman]

The noise is a hum.
With no guitar plugged in, the hum is there. If as I crank the volume, the hum does not get any louder. I can hear the usual hiss from a cranked amp slowly appear, but the hum stays the same at 0 or volume at 10.
I'm going to switch out the 3 pinkish caps mentioned by cyclone and take it from there.

Probably the power supply filter caps have gone stale.

[Jonny toetags]

Here's a more detailed shot of the filter caps:



They've obviously been switched out along the years. I have four 22uf's.
Should I just switch them all out for the same values or should I change anything?
I'm not sure if this they are proper filtering for an Ampeg.

[soundguruman]

You have to figure out what model, to know what caps really belong.
There is more than 1 reverborocket...there are several.
http://www.turretboards.com/layouts_...ampeg_r12r.gif

What tubes does the amp have in it? That will help identify which version you have...

The thing is:
Old tubes can hum too.
And old ampegs can have hum, just because of design and layout.

BUT in a really old amp, it is not unusual to have the power supply filters going bad.

So figure out which schematic matches your amp.
And no, it will not hurt to change them all. I would probably change them out for the same reason.

I mean electrolytic caps do go bad with age, for sure.

[Jonny toetags]

It's an R12R, 008539.
Right now it has (from rear, L to R): two of the strange tubes, two 12AX7's and then a pair of RCA 7868's.
Are 7868's the right tubes for this model? All the pics I've seen online have had 75914a's

[Jazz P Bass]

The RCA 7868 tube used a Noval socket.

It is 'basically' the same tube as the 7591A.

This schematic may be close: http://www.turretboards.com/layouts_...ampeg_j12r.gif

[Jonny toetags]

Have my 7591A's on order!

Quick filter cap question. This amp has had the original filter caps removed and has 22uf's instead.
I want to replace those but all I have are 33uf's on hand. Would it make that much difference if I used those?

[52 Bill]

Have my 7591A's on order!

What tube sockets are in the amp? Will the 7591A fit in there?

Using 33uF instead of the 22uF will probably work just fine.

[Jonny toetags]

I'm told they will fit but stretch out the pin sockets so I won't be able to go back to the NOS tubes.
I plan on doing the caps first to see if they are creating the hum.

What tube sockets are in the amp? Will the 7591A fit in there?

Using 33uF instead of the 22uF will probably work just fine.