I have a question in regards to upgrading Peavey CS 800 electrolytics

[OMNIFEX]

Greetings!

One of my CS 800 amplifiers is in need of an electrolytic replacement. It is the oldest (1977) out of my inventory and, still uses all it’s original parts. The amplifier works fine with the exception of a weak (declining torque strength) fan that I will be replacing today. The capacitor upgrade is merely based upon being 32 years of age.

I was curious if I increased the capacitance in this amplifier would I notice an improvement on the bass response. This amplifier, with the eleven others are used in bridged mono for sub duty ranging from 100 – 25.5 Hz (+/- 3dB).

Has anyone taken it upon himself or herself to increase the capacitance on these old amplifiers? Observing the schematics, I’ve noticed the capacitors are wired in series, which results in a micro fad of 7,500.

What I was proposing to do is increase the micro fad from 7,500 to 15,000 or even 30,000

If the results are stellar, I will upgrade the other four as well. Please bear in mind that the amplifier in question is the Non-DDT version.

Also,

Would anyone know if the CS 800X follows the same topology in terms of ratings and, use the series scheme as well? I do not have the schematics on the CS 800X to verify.

Cheers!

[wg_ski]

If I could find a pair of 30kuF, 47kuF, or 68kuF caps that would fit, I'd drop them in without a second thought. Are you running them at 8 ohms bridged or 4? At 4 ohms bridged, the existing 15kuF caps are marginal - you really need 20kuf on each rail or better to properly filter a supply for 2 ohm operation. I know, the CS800's don't recommend this, but the truth is those amps will tolerate it a lot better than an equivalent modern one will (which is probably why you're still using them).

[OMNIFEX]

Thank up wg_ski!

They are used @ 4 ohms bridged mono. However, based on the impedance rise/dips of the subs at the given frequencies the amplifier sees no less than 3.9 ohms minimum.

I haven’t had much luck online with mouser, digi-key and, so forth. So, I have decided to venture to a few electrical shops in town on Saturday.

Cheers!

[wg_ski]

Mouser or Digi-Key could get the for you - for a price - and a very large MOQ. I was thinking surplus outlets. 100V are bit more difficult to find - I have 16 28kuF/150V, a handful of 200v at similar capacitance, and four 44kuF/100V but they're too tall to fit in a CS-800. Plenty of 68kuF/75V in the right form factor but that's not quite enough voltage.

[llwhtt]

Omnifex,

I can email you the 800X schematic if you want, need the original 800 also?

Craig

[llwhtt]

Omnifex,

I just pulled the 800X schematic up and it uses 10KUF@75V. One caution on increasing the power supply caps, years ago Peavey added triac to the input of the power transformer, took the load off of the power switch. You might want to check your amps to see if they've been modified or even possibly manufactured that way, not sure what year they started that. Its pop-riveted to the bottom of the chassis, inside of course.

Craig

[OMNIFEX]

Thank you Gentlemen.

Originally posted by wg_ski
Mouser or Digi-Key could get the for you - for a price - and a very large MOQ. I was thinking surplus outlets. 100V are bit more difficult to find - I have 16 28kuF/150V, a handful of 200v at similar capacitance, and four 44kuF/100V but they're too tall to fit in a CS-800. Plenty of 68kuF/75V in the right form factor but that's not quite enough voltage.

I'm going to stop by the electrical shop where I purchased 6 Gauge SO cable 10 years ago. At the time, they stocked a lot of industrial supplies.

Originally posted by llwhtt
Omnifex,

I can email you the 800X schematic if you want, need the original 800 also?

Craig

That is a very noble of you. Thank you. I currently have the CS 800 “A” Series schematic. I would imagine the B & C versions are the same in the power supply section with the only addition being DDT.

Originally posted by llwhtt
Omnifex,

I just pulled the 800X schematic up and it uses 10KUF@75V. One caution on increasing the power supply caps, years ago Peavey added triac to the input of the power transformer, took the load off of the power switch. You might want to check your amps to see if they've been modified or even possibly manufactured that way, not sure what year they started that. Its pop-riveted to the bottom of the chassis, inside of course.

Craig

I haven’t thoroughly examined the CS 800X other than cleaning heat sinks once a year. I own all the excluding the switch mode version so, I will open one of each to find out.

You should see a pm with my email address arriving shortly.


Cheers!

[llwhtt]

Only the older ones will have or not have the triac, it's already in the "X".

Craig

[SQLGuy]

I was filter cap shopping recently. I found some of the best prices and selection here: http://capacitor.tedss.com

Overall, somewhat cheaper than both Mouser and Digi-Key.

Cheers,
Paul

[OMNIFEX]

Originally posted by llwhtt
Only the older ones will have or not have the triac, it's already in the "X".

Craig

Fair enough. Cheers for the schematic.

Originally posted by SQLGuy
I was filter cap shopping recently. I found some of the best prices and selection here: http://capacitor.tedss.com

Overall, somewhat cheaper than both Mouser and Digi-Key.

Cheers,
Paul

That is an excellent link. Thank you. It is the first online store I've encountered that brings forth a wide variety of capacitors to choose from based on my needs.