Need Advice on Capacitor Replacement + Other

Hey all. As some of you may know from a previous post, I'm working on a Fender Rhodes Suitcase Piano with a 100W Peterson amplifier. I have been able to locate many of the parts I need to restore/repair the amp, but I'm having a couple issues with finding some specific electrolytic capacitors, as I'm trying to replace all of them since they're so old. I know my questions may seem obvious to most of you, but they're not to me, as I'm a novice and still learning.

The problem I'm having is with the +/- 15 Volt Regulator board. On this board are 4 capacitors, 2 @ 1000uf and 2 @ 500uf, along with 7815/7915 regulators and 3A diodes.

My question is can I go up in capacitance? Or, even lower (use a 470uf cap in place of the 500uf). All 4 of these capacitors are rated at 90C. The only capacitors in these values I have been able to find are rated at 85C. They are axial. I have debated about installing radial caps, but am apprehensive about the leads being too short. I "can" drill some new holes in the board in order to install 3 of the radial caps, but on one there is really no way that I can do this. I'm trying to stick with axial caps to make the job easier. I would like to use 105C , axial caps, but I can only find higher capacitance value caps: 560uf, 680uf, 1100uf, 1200uf and a lower 470uf. I know I can go higher in voltage, but can I go higher (or lower in the case of the 500uf cap) in capacitance without putting strain upstream on other components?

The other question I have is about some transistors on each of the power boards. They are TIP29B and TIP30B. I want to replace these too, since I have a burnt 7815 on the regulator board. Odds are they're good, but I still want to replace them since they're inexpensive. Can I use TIP29C and TIP30C even though they're rated for a higher voltage? I assume I can, but would like to hear it from people more knowledgeable thaan me.

Sorry if these questions seem stupid and should be obvious to me. They're not.

Here's some pics of each of the boards and the schematic.

Thanks for your help.
 

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jean-paul

diyAudio Moderator Emeritus
2002-09-20 7:20 am
Germany
Definitely stay with axial types. C1 and C2 can be 2200 µF 35V if you like. They possibly fit better as caps have become physically smaller by the years. If 2200 F 50V fits even better than get those. I would choose low ESR caps for these. C3 and C4 should be less than 500 µF IMO. I would use 100 µF 50V here. I would also replace the 7815 and 7915 for current Onsemi versions as they're less noisy now.

* Your board has a 7920 instead of a 7915 !
 
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Cortez

Member
2002-12-26 9:45 am
Hungary
The other question I have is about some transistors on each of the power boards.
They are TIP29B and TIP30B. I want to replace these too, since I have a burnt 7815
on the regulator board. Odds are they're good, but I still want to replace them since
they're inexpensive. Can I use TIP29C and TIP30C even though they're rated for a higher
voltage? I assume I can, but would like to hear it from people more knowledgeable thaan me.
Yes you can but if you measure them with the simple diode tester mode you can spare the new ones.
 
Definitely stay with axial types. C1 and C2 can be 2200 µF 35V if you like. They possibly fit better as caps have become physically smaller by the years. If 2200 F 50V fits even better than get those. I would choose low ESR caps for these. C3 and C4 should be less than 500 µF IMO. I would use 100 µF 50V here. I would also replace the 7815 and 7915 for current Onsemi versions as they're less noisy now.

* Your board has a 7920 instead of a 7915 !


I think that UC7920 number is something different. The 7915 has a UC number of UC8040. Maybe those were other used numbers for exports? I don't know.

I don't understand the cap values you suggest. From my reading on the subject on the Internet it seems that going lower on capacitance is never a good idea, at least as much as the different between 500uf and your suggestion of 100uf is. As far as using a 2200uf in place of the 1000uf, I just don't know. Seems like a large increase. I have read in a few different places that going up in capacitance is OK in most cases, but NEVER lower. I'm even more confused now.
 

Cortez

Member
2002-12-26 9:45 am
Hungary
Yep!
Caps: these values are so critical as you think.
You can use values as you was sugguested.
100uF: after a regulator there is no need for a big filtering.
Sometimes there is just a few uF C here...
Check the datasheet for recommendations or similar builds to check values.
 
Axial lead caps are very limited stock. 85 deg C is what is stocked now. Many radial lead caps can be bought with lead lengths of inch and a quarter or more, read the data sheet. You can glue them to the board with weatherstrip adhesive. I wouldn't go lower than the temperature rating on the board already.
Seventies caps without tolerance were +80 -20% so I would pretty freely use a 470 or a 560 for the obsolete 500 value. Caps are +-20% now. 1000 uf is very common.
A transistor is two diodes, ~.6 v (or 600 "ohms") forwards, 1999 or ---- backwards. Sometimes you have to lift the base to get a reading with a DVM. Usually if you get different readings forwards and backwards, the transistor is okay. 78xx fail pretty often, especially if not provided with a heat sink orginally. Hint.
Transistors don't age much. Zener diodes do, which 78xx contain. But zeners aren't as bad as electrolytic caps, there is no rubber or water.
I wouldn't go up 110% in value on caps without reengineering for surge protection ahead of the feeding part.
I like to buy new caps with service life rating of >3000 hours, so I don't have to replace the e-caps every 8 years like I had to do when I was buying parts at the TV repair supply store. 500 hour caps are most of stock, and mostly what people buy, but I don't intend to throw away the appliance in 3 years because the case went out of style. Digikey has the hours in the selector table, and newark you can request it be shown. Height can be critical, make sure you check for that also.
If the radial caps absolutely won't reach, put in a cinch type solder terminal strip like a 56A or 53, on #6 or #4 screw with elastic stop nut. Use extra wire as required. Be sure to drill where there is no metal land. Use a lot of light to spot the place. I use a hand crank drill for this, $2 at the flea market. Fits those tiny #27 or #32 drills better than a 3/8" chuck.
Unfortunately cinch terminal strips come from electronicsurplus.com apexelectronic.com tubesandmore.com triodeelectronic.com or mcmelectronic.com I wouldn't buy e-caps from any of those houses. Surplus e-caps are old and mcm doesn't list the brand and manufacturer part number to sort out the short life ones. Screws can be had from the majors, especially in 3 mm or 4 mm, but elastic stop nuts are mcmaster.com mostly. I buy bags of 50 or 100 for $2-3 but freight is $7 minimum. Get the drills while you are at it, those are not a hardware store item. If buying mm screws you'll have to buy mm drils, I don't know those numbers.
Enjoy your music. I've tweaked the pots on a Hammond H100 glock percussion to sound somewhat like a Rhodes electric piano. A much cheaper instrument than a real Fender Rhodes.
 
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Many radial lead caps can be bought with lead lengths of inch and a quarter or more, read the data sheet..

I have been through countless datasheets and every one of the radial caps I have looked at seem to have lead lengths of 15mm/20mm respective to their polarity. I haven't seen any with leads as long as 1 1/4 in. Where do you find those? If I could find leads that long, I wouldn't have to do any drilling to install radial caps in pace of the axials.

You can glue them to the board with weatherstrip adhesive. I wouldn't go lower than the temperature rating on the board already.

Would a little bit of hot glue work, also?

Seventies caps without tolerance were +80 -20% so I would pretty freely use a 470 or a 560 for the obsolete 500 value. Caps are +-20% now. 1000 uf is very common.

I've found a few 470uf caps in the axial configuration. Maybe one 560uf cap.


I wouldn't go up 110% in value on caps without reengineering for surge protection ahead of the feeding part.

That's pretty much my line of thinking and why I posed the question to start with. Still, 110% of 500uf is over 1000uf. Are you saying I could safely use 1000uf caps in place of the 500uf cap?

I like to buy new caps with service life rating of >3000 hours, so I don't have to replace the e-caps every 8 years like I had to do when I was buying parts at the TV repair supply store. 500 hour caps are most of stock, and mostly what people buy, but I don't intend to throw away the appliance in 3 years because the case went out of style.

If available, I have the intention of getting caps with the greatest service life that I can find.

If the radial caps absolutely won't reach, put in a cinch type solder terminal strip like a 56A or 53, on #6 or #4 screw with elastic stop nut.

I don't think I'm familiar with this technique. Is this some type of strip that attaches (screws) to the board and then the leads of the cap are attached to it? Right now, I can replace 3 of the 4 caps on the reg board with radials by drilling new holes. On the other one, though, because of the trace configuration, there is just nowhere to drill new holes. If I could find the radials with longer leads, that may solve that problem, though.



Would another acceptable way to utilize a radial cap in place of an axial cap be to cut off the existing leads of the axial cap and leave them in place, and then attach the leads of the radial cap to the existing leads by "looping" them together at the ends and soldering?

Thanks for the great advice Indianajo. I'm going to check out those cinch strips and see if that may be something I want to utilize.
 
Still, 110% of 500uf is over 1000uf. Are you saying I could safely use 1000uf caps in place of the 500uf cap?
I don't think I'm familiar with this technique.
No. 500 uf + 110% is 1050 uf. I'm saying 470 or 560 will replace 500.
I don't know about hot melt guns; they have always been made in ***** and I never bought one.
I just put some caps in a power supply for an acquaintance. Panasonic eeufr, nichicon uvr, nichicon upt, nichicon uhe, all had leads about inch or inch and a half long. The plus one is longer.
Snap-in caps have short leads, about half an inch. The bigger sizes, 2200 uf & up.
I made up the cinch terminal strip thing, I don't check everything I do on the internet.
I also have hooked new caps to hooks on old leads, left in the PWB. Keeps me from de-mounting PWB's from some of my organs, and diving into 26 ga wirewrap, very obsolete technique. However, organs don't get gigged much and roady load shock is not an issue. It would be an issue for a Fender Rhodes that was gigged.
I use newark mostly, the most recent I got from digikey because they had the IC I needed. I live 1 day away from newark in SC by UPS surface - in by 9 AM here by 5pm next day quite often. Digikey is in MN, Mouser is in TX. Newark is waaaay cheaper on metal film resistors from THA, BRA, TWN, which I am stocking up on before the leaded ones disappear. 20 at a time usually <$1.
 
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No. 500 uf + 110% is 1050 uf. I'm saying 470 or 560 will replace 500.
I don't know about hot melt guns; they have always been made in ***** and I never bought one.
I just put some caps in a power supply for an acquaintance. Panasonic eeufr, nichicon uvr, nichicon upt, nichicon uhe, all had leads about inch or inch and a half long. The plus one is longer.
Snap-in caps have short leads, about half an inch. The bigger sizes, 2200 uf & up.
I made up the cinch terminal strip thing, I don't check everything I do on the internet.
I also have hooked new caps to hooks on old leads, left in the PWB. Keeps me from de-mounting PWB's from some of my organs, and diving into 26 ga wirewrap, very obsolete technique. However, organs don't get gigged much and roady load shock is not an issue. It would be an issue for a Fender Rhodes that was gigged.
I use newark mostly, the most recent I got from digikey because they had the IC I needed. I live 1 day away from newark in SC by UPS surface - in by 9 AM here by 5pm next day quite often. Digikey is in MN, Mouser is in TX. Newark is waaaay cheaper on metal film resistors from THA, BRA, TWN, which I am stocking up on before the leaded ones disappear. 20 at a time usually <$1.

Man, I have been all over the place on the Internet. I have been to Mouser, Digikey, Newark, Allied, Tedss. I can't find any suitable caps. When I do find a 500uf or 560uf, they are rated at 85C for ones in stock. If they list a 500uf or 560uf that is 105Cor better, it is a non-stock item or there are minimum purchase quantities, sometimes in the 100s of pieces. I feel like I'm running around in circles. I can't find any radials with long leads anywhere. All the datasheets show lead lengths to be 15mm for the neg and then 4mm longer for the pos. In the best scenario, that would allow a reach of around 40mm. Sure, they say the lead dimensions are minimums, but who knows if you will get them with longer leads. Can't bank on hope.

Any suggestions as to caps to use?
 
Those were part numbers I got out of dealer stock. The first letters are the series code - I don't buy 500 hour caps. 470 uf and 1000 uf are dirt common.
On newark I put a minimum & maximum capacitance , a minimum & maximum voltage, stock, no direct ship ( from UK for $25) let it rip. I don't put life rating because they have them alphabetical and space counts, so they are all jumbled up if you put a minimum on that. The temperature, sometimes you can find 105 C, sometimes you find 140 in automotive grade, sometimes you're stuck with 85. I don't have a problem with 85 C, but organs are roomy inside.
Digikey I have to control click several capacitances and voltages. Same with mouser. Haven't bought from alliedelec since 1982? before debit cards were invented.
I fished a 1000 uf @ 50v out of the carpet today, nichicon upm1h102 I bought in 9/15 for $.85 from newark.
Today newark have got Vishay axial mal21381 5000 hr @ 105 C for $4 or radial Panasonic eeufc 5000 [email protected] for $1.09. I think I saw friday they had nichicon 560 @ 50 long life for $.37 same as I put in this guy's power supply.
Maybe the voltage you're picking is obsolete. You can't hardly get anything under 25 v these days, and I've noticed 63 v is disappearing, 80 is scarce, the choices are 50 and 100 v.
 
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Ok. After going through a bunch more capacitors, I found a couple that may work. I narrowed it down to the following 2 choices:

The first choice are radials.

To replace the 500uf caps:
MAL214651681E3 Vishay BC Components | Capacitors | DigiKey

To replace the 1000uf caps:
MAL214691125E3 Vishay BC Components | Capacitors | DigiKey


If I go with axials:

To replace the 500uf caps:
MAL211890509E3 Vishay / BC Components | Mouser

To replace the 1000uf caps:
MAL211817102E3 Vishay / BC Components | Mouser



Any opinions?
 
Those caps are all axial, not radial.

What are you referring to? The caps on the pic of the reg board I attached in my first post? I know they're axials. I'm having trouble finding axial caps with the correct capacitance and temp rating. They are 90C caps. I don't want to use 85C caps. I can use radials, but will have to drill new holes in the traces on the board to install them. Doable, but more work. Would rather go with axials. Less work.
 
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jean-paul

diyAudio Moderator Emeritus
2002-09-20 7:20 am
Germany
In 2016 it is plain wrong practice to use 500 µF after regs and I would certainly not use even larger values. With the caps of 30 years ago it was not a problem. Note that modern electrolytic caps have lower ESR than the older ones anyway. Please read datasheets and use recommended values for caps after regs. About replacing the 1000 µF caps for 2200 µf : it is BS that fuses will blow etc. It could be like that with 10,000 µF or the like. With 2200 µF ripple will be somewhat lower and they will fit physically. Using higher rated (in voltage ) caps won't harm in any way so you could play with that idea and use the physically most fitting ones. Be them 50 or 63V types. I would use a small dot of RTV to attach them to the board (electronics grade RTV that is).

* please think that time has not stood still. You have to adapt to modern fresh capacitors with way better specifications. To think that everything must be "original" is fear of the unknown and neglect of specifications at the same time ;)
 
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