A friend brought to me a 1977 Earth Sound Research Concertmaster P.A. amp and asked me to go through it since it needed some work to get it going. It's operating now, but I'm wondering about all the 49- to 50-year-old e-caps that are in there. Since he also handed me some schematics, I noticed that the schematic shows for the two main filter caps, a value of 4500uF/50v. What I found was a pair of 6800uF/50v. I can't tell if these are original or replacements. I'm guessing that they are replacements, and I cannot find a date code on them. If I were to replace them, should I use original spec? Is there any good reason for the higher capacitance e-caps in there? A cap with a 35mm diameter is the proper fit, and with solder lugs too. I could save my friend some money by using a 35mm-wide snap-in style and strip the wire leads about a 1/2" and wrap around the cap's snap-in leads for one third of the cost... Bad idea?
Higher Value Filter Caps Installed In SS Amp
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Higher Value Filter Caps Installed In SS Amp
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Greg
Re: Higher Value Filter Caps Installed In SS Amp
It will be far more reliable if all of the electros are replaced by new, fresh ones. I have run into this before with 50-60 year old Vox amps. These are prone to Technician H@ll when the owner turns down an expensive replace-them-all job, and only one or two failing ones get replaced. Then a week, month, or year later, the next one fails; then the next, then the next.
SS amps with SS rectifiers are not sensitive to bigger filter caps like vacuum rectifiers are. There is no hard-and-fast limit. I would put in replacements that are (1) the same or larger voltage rating (2) the same physical dimensions to be easily mountable and (3) as much capacitance as can be reasonably and affordably obtained from a quality capacitor maker.
SS amps with SS rectifiers are not sensitive to bigger filter caps like vacuum rectifiers are. There is no hard-and-fast limit. I would put in replacements that are (1) the same or larger voltage rating (2) the same physical dimensions to be easily mountable and (3) as much capacitance as can be reasonably and affordably obtained from a quality capacitor maker.
"For every complex problem there is an answer that is clear, simple, and wrong"
H. L. Mencken
H. L. Mencken
Re: Higher Value Filter Caps Installed In SS Amp
I haven't seen "Earth" amplifiers like that in many years. As a 16-year old, I cleaned out a barn that had a stack of Earth amps in it, many partially disassembled.
Let's just say, they bear an uncanny "resemblance" to Peavey amps of the same era. As in, direct, rip-off copies.
I patched together bits of this and that to make as many working amps and PA's as I could from various front and back panels and head sleeves, even mated some to actual Peavey front or backs and fobbed them off for whatever I could get for them.
On the capacitor question: In this application, like RG says, it is a game of horseshoes and hand grenades, close is good enough. With as much room as you have there, feel free to be creative in value, voltage, mounting, and most of all, budget. Because Earth absolutely, didn't care much about "specs" just whatever made it go.
To be honest, I would probably decline to work on it. You'll wind up married to it.
Let's just say, they bear an uncanny "resemblance" to Peavey amps of the same era. As in, direct, rip-off copies.
I patched together bits of this and that to make as many working amps and PA's as I could from various front and back panels and head sleeves, even mated some to actual Peavey front or backs and fobbed them off for whatever I could get for them.
On the capacitor question: In this application, like RG says, it is a game of horseshoes and hand grenades, close is good enough. With as much room as you have there, feel free to be creative in value, voltage, mounting, and most of all, budget. Because Earth absolutely, didn't care much about "specs" just whatever made it go.
To be honest, I would probably decline to work on it. You'll wind up married to it.
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Stevem
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Re: Higher Value Filter Caps Installed In SS Amp
Yup sure does look like a peavey !
Good that it’s not like that same era Sunn amps with PI / driver transformer in terms of sound, although that arrangement does make it easier to troubleshoot output stage issues.
I have over the years repaired a bunch of Kustom amps and the large computer grade can filters that they where made with amazingly seem to last forever 95% of the the time, even the ones made as far back as 1968 and 67.
They were originally made with 4500 uf 50 volt filters ( ran on 40 volts) but these days it’s hard to get them in the UF rating so I go with 6800 or even 10000 .
I also like to place a .22uf cap and a .022 cap across each filter.
Sounds better to my ear.
Since a lot of these old SS amps have no over current protection in the event of a short on the output I always try after a rebuild to talk the owner into installing this circuit that if I recall right I did lift from a Peavey amps.
Good that it’s not like that same era Sunn amps with PI / driver transformer in terms of sound, although that arrangement does make it easier to troubleshoot output stage issues.
I have over the years repaired a bunch of Kustom amps and the large computer grade can filters that they where made with amazingly seem to last forever 95% of the the time, even the ones made as far back as 1968 and 67.
They were originally made with 4500 uf 50 volt filters ( ran on 40 volts) but these days it’s hard to get them in the UF rating so I go with 6800 or even 10000 .
I also like to place a .22uf cap and a .022 cap across each filter.
Sounds better to my ear.
Since a lot of these old SS amps have no over current protection in the event of a short on the output I always try after a rebuild to talk the owner into installing this circuit that if I recall right I did lift from a Peavey amps.
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When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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syscokid
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Re: Higher Value Filter Caps Installed In SS Amp
Thank you all for the valuable responses. And yes, it’s very Peavey-like. I got the OK to at least recap the rear panel: The 2 main filtering caps and the 4 small e-caps of the power supply board. If he really likes it, he might ask me to recap the front panel’s 23 small e-caps.
To get this amp operational, I needed to install a new AC cable. For whatever reason, the old cable was snipped off at the strain relief. All the pot controls needed to be cleaned out and vigorously rotated. Most were very scratchy and some were losing signal at different points of their rotation. All the jacks were dirty with corrosion between the nuts, washers, threaded shaft, and their contact blades. All good now though!
I got a good chuckle from reading the label on the amp’s reverb tank: And finally, I found an interesting read on the short history of Earth Sound Research:
http://www.pedalhaven.com/history-earth ... mplifiers/
To get this amp operational, I needed to install a new AC cable. For whatever reason, the old cable was snipped off at the strain relief. All the pot controls needed to be cleaned out and vigorously rotated. Most were very scratchy and some were losing signal at different points of their rotation. All the jacks were dirty with corrosion between the nuts, washers, threaded shaft, and their contact blades. All good now though!
I got a good chuckle from reading the label on the amp’s reverb tank: And finally, I found an interesting read on the short history of Earth Sound Research:
http://www.pedalhaven.com/history-earth ... mplifiers/
You do not have the required permissions to view the files attached to this post.
Greg
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Stevem
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Re: Higher Value Filter Caps Installed In SS Amp
Those aluminum pins in those inter board Molex connectors tend to tarnish up and get loose.
Give them a shot of cleaner/ lube and carefully pinch the female recivers a bit tighter.
Give them a shot of cleaner/ lube and carefully pinch the female recivers a bit tighter.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Higher Value Filter Caps Installed In SS Amp
Many of those Earth amps not only looked like Peavey, but literally photocopied their circuit board layouts, including part numbers, only masking out anything that actually said, "Copyright Peavey" on it.
But unlike Peavey, they tended to stuff them with whatever parts they could sweep up.
This one already has some ECG-xxxx parts in it in the photos. The cord being snipped off is probably a sign from a former tech...
But unlike Peavey, they tended to stuff them with whatever parts they could sweep up.
This one already has some ECG-xxxx parts in it in the photos. The cord being snipped off is probably a sign from a former tech...
Re: Higher Value Filter Caps Installed In SS Amp
What do think the former tech might have meant by doing that? I eventually found the Facebook Marketplace ad that my friend made the purchase through. Asking price was $50!
I remember years ago, I received a recall notice on a dehumidifier we had bought. If we wanted a full refund, we were instructed to cut off the power cord and send proof by attaching a photo to the reply email.
Greg