Early 60's Ampeg Reverberocket: need help with noise

[soundguruman]

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?

It would probably be better with 33.

[52 Bill]

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.

Please check the sockets, the 7591A tube has an 8 pin octal base, while the 7868 has a 9 pin noval base.

[Jonny toetags]

Please check the sockets, the 7591A tube has an 8 pin octal base, while the 7868 has a 9 pin noval base.

Thanks for the heads up Bill. I didn't even know that!

[Jonny toetags]

Little update:

I recapped the amp over the weekend and also fixed a few suspicious solder joints.
It still has a hum (almost sounds like a ground hum), but it's not as intense. I did notice that the amp sounds and feels a bit better, so the cap job didn't hurt.
Not sure if this is helps any, but the hum is present with no cable plugged in, and never gets louder as volume increases.
Speaking of volume....with the volume at 0...there is still some sound. Worth fixing?

I'm wondering if a set of NOS 7868 tubes would help this amp....but it's a 100$+ gamble.

[52 Bill]

From my personal experience with Ampegs of this vintage, the grounding of the filter caps plays a large part in the background hum. When ever the grounding point of the main filter caps is moved the hum will increase to sometimes dramatic levels.

I can't tell from your photos, but if the grounding point is not at the original spot it may be the cause of your hum.

As for new tubes, how bad are the old ones?

[Jonny toetags]

From my personal experience with Ampegs of this vintage, the grounding of the filter caps plays a large part in the background hum. When ever the grounding point of the main filter caps is moved the hum will increase to sometimes dramatic levels.

I can't tell from your photos, but if the grounding point is not at the original spot it may be the cause of your hum.

As for new tubes, how bad are the old ones?

I'm going to try and take a few pics when I get home later.
I'm pretty sure the grounding point would have been moved since the caps were changed to a tagboard.
What would be the proper grounding for this amp?

[Jonny toetags]

Here's a few extra pics i took:

[52 Bill]

I am assuming that the added radial caps are there to replace the large can cap that is still mounted to the chassis, correct? If this is so, what values are in the original can cap? The posted schematic shows 70/40/40.

It appears that the two new caps that are near the top of the chassis (opposite the tubes) are wired in series. Is this correct?

[Jonny toetags]

I am assuming that the added radial caps are there to replace the large can cap that is still mounted to the chassis, correct? If this is so, what values are in the original can cap? The posted schematic shows 70/40/40.

It appears that the two new caps that are near the top of the chassis (opposite the tubes) are wired in series. Is this correct?

Yes..the can is there for show only. I pretty certain the original caps exploded due to the goo in the chassis
It would have been what the original schematic shows, so like you I was guessing 70/40/40

Here's a little diagram of the wiring I did.

[52 Bill]

Yes..the can is there for show only. I pretty certain the original caps exploded due to the goo in the chassis
It would have been what the original schematic shows, so like you I was guessing 70/40/40

Here's a little diagram of the wiring I did.
[ATTACH=CONFIG]27846[/ATTACH]

The cap can is marked with the capacitance and the voltage ratings, what does it read?

[Jonny toetags]

the cap can is marked with the capacitance and the voltage ratings, what does it read?

60 mfd @ 450v
40 mfd @ 450v
10 mfd @ 450v
20 mfd @ 25v

[52 Bill]

60 mfd @ 450v
40 mfd @ 450v
10 mfd @ 450v
20 mfd @ 25v

Okay, the first problem is the first replacement cap is too small. Your first two caps in series equal a 16uF cap. They should be in parallel so they will equal 66uF. Be sure that the voltage ratings are high enough to match the original one.

Is the original can cap mounted to the chassis on a fiber spacer? If it is, is the original ground wire still connected to the can?

[Jonny toetags]

Okay, the first problem is the first replacement cap is too small. Your first two caps in series equal a 16uF cap. They should be in parallel so they will equal 66uF. Be sure that the voltage ratings are high enough to match the original one.

Is the original can cap mounted to the chassis on a fiber spacer? If it is, is the original ground wire still connected to the can?

Here's is a pic from before I did the cap job and some cleaning. I have two 33uF's in parallel on that other piece of tagboard.


The original can cap isn't wired to anything.

[52 Bill]

Here's is a pic from before I did the cap job and some cleaning. I have two 33uF's in parallel on that other piece of tagboard.

The original can cap isn't wired to anything.

So the two 33uF caps in parallel are connected to the first node of the power supply? What are the two caps in series connected to?

Is there a black ground wire still connected to the can cap?