Greetings. I have a Mc2500. The amplifier board was badly repaired a long time ago and now has become unusable. I do not know if I'll
be able to salvage the op amps. The rest of the amplifier is however still in good shape. I am making a new amp board myself for both channels
with new components as there aren't any stock available in the company and the used boards on online auction sites, look dubious. I need to
know however, what brand/type of resistors and capacitors did the manufacturer use in those Mc2500 amplifiers. I need to purchase new
components to make the new board but do not want to end up spoiling the original tone of the amp. Also, if I can't salvage the op amp on the board,
what is the best substitute for the original op amp? If someone knows, kindly advise me on this issue. This means a lot. Thank you.
be able to salvage the op amps. The rest of the amplifier is however still in good shape. I am making a new amp board myself for both channels
with new components as there aren't any stock available in the company and the used boards on online auction sites, look dubious. I need to
know however, what brand/type of resistors and capacitors did the manufacturer use in those Mc2500 amplifiers. I need to purchase new
components to make the new board but do not want to end up spoiling the original tone of the amp. Also, if I can't salvage the op amp on the board,
what is the best substitute for the original op amp? If someone knows, kindly advise me on this issue. This means a lot. Thank you.
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Apart from those bent down black parts next to the lefthand edge, which I don't recognize, I don't see any exotic components whose replacement by industrial grade parts may 'spoil the original tone'. Anyway, there's an original Signetics NE5534 opamp which may be hard to find these days from that manufcaturer. I think a TI one may also work.
Best regards!
Best regards!
Those look like carbon film resistors about 1/4 watt except the big ones 1 watt. I find resistors from vishay, welwyn, TE connectivity, farnell(newark) multicomp are usually produced in countries that don't have so many lies on the QA paperwork as the source of 99% of electronics. Watch the wattage on the vishays, they rate the wattage now at about 300 F which would burn any circuit board. Buy the resistors rated 300 v or larger to get the wattage that won't run too hot. 1 or two watt, you can also look at the length to make it match.
Those black box 200 ohm resistors, better buy 3 watt. Don't have to be square.
I mostly buy metal film resistors which hit the market in the 2000's after this board but have less thermal noise than carbon film in the sizes over 100 kohms.
Wima capacitors are still available and well respected. Not at any of the major distributors in the US, some boutique house. Polyprophylene dielectric is usually the least distorting, don't buy polyester which is fine for power supplies but not sound. Those black capacitors I don't recognize the logo, but panasonic, kemet, vishay polypropylene film are okay. J is about 200 v, maybe more than required.
I've used TI 5532 which is the dual version of op amp 5534, had no problems with it.
The black device lower left looks like an inductor. You had better salvage that.
Those black box 200 ohm resistors, better buy 3 watt. Don't have to be square.
I mostly buy metal film resistors which hit the market in the 2000's after this board but have less thermal noise than carbon film in the sizes over 100 kohms.
Wima capacitors are still available and well respected. Not at any of the major distributors in the US, some boutique house. Polyprophylene dielectric is usually the least distorting, don't buy polyester which is fine for power supplies but not sound. Those black capacitors I don't recognize the logo, but panasonic, kemet, vishay polypropylene film are okay. J is about 200 v, maybe more than required.
I've used TI 5532 which is the dual version of op amp 5534, had no problems with it.
The black device lower left looks like an inductor. You had better salvage that.
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Thanks Kay, Indianajo and IIwhtt. Plenty of ceramic disc capacitors used here. Do I buy new CD capacitors for the new board or replace them with Wima MKP? For the metal film, I can always use Vishay RN55 and Z Foil resistors but as for the carbon film, am not sure about which ones to use.
Yes, for a new build you can substitute ceramic disc capacitors by Wima MKP's, simply because they belong to the best capacitors worldwide. Bt why substituting metal film resistors by others? Please don't believe that 'resistor sound' voodoo snake oil BS. It would exclusively part you with your hard earned money. Metal film resistors are the best and most reliable ones with the closest tolerances that one can buy for reasonable money. So, you'd substitute these carbon resistors by metal film ones also.
Best regards!
Best regards!
ceramic disk caps can't be substituted by polypro film. Too much inductance. Aerovox vishay kemet are reliable ceramic disk brands.
Insisting on vishay dale rn55 metal film resistor is a good way to run your costs up. By allowing any of the metal film brands listed in post #3 I can usually buy 2-3 watt resistors for $5 a hundred instead of $.40 each. 600 mw usually $1.20 a hundred. Where 10% resistors were used, I also allow 1% resistors within the tolerance band. Newark usually has some end of bin bargain going, at least 33% of the time. I use the min/max selector function to show those 1% off center values instead of insisting on the EIA standard value. 10 % tolerance these days means 100 of exactly 8 1/2% low, usually. Brands I never bought again, International, zicor? always from land of counterfeiters. I see mouser has dropped the brand from ***** they used to stock all the time. Wonder why?
Neither newark, digikey, or mouser carry elna electrolytics. I've bought ~800 electrolytics or so reworking amps & electric organs, have none of those. No problems, no repeat repairs since 2008. No "audio" 300% premium lines, either. Nichicon panasonic rubicon vishay kemet make a good industrial cap if you buy the long lifers, no need for "audio" grade at a rediculous premium. All also sell a 500 hour cap if a repair shop wants the customer to come back with a broken product again in 5 years. The 500 or 1000 hour service life caps show up first in the list since they are the cheapest. I leave my main amp on 2000 hours a year listening to the radio, used to burn through 500 hour caps from the TV repair shop in 5-8 years. Back when individuals could not buy from real distributors, before debit cards.
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Good day,
Thank you for your replies Indianajo and Kay Piranha. My apologies for responding late. Am recovering from an accident and was immobile for some time. During this time, the technician building a new board for me has come up with the parts list for the board. You were right. There is a considerable amount of Carbon Film Resistors and maybe 5 Metal Film resistors. Do I follow the exact configuration and replace them with Carbon Film or replace everything with Metal Film? What brand of resistors do you recommend? I am not very tight with budget but at the same time, do not want to buy into unnecessary expenses. Even if the resistors cost more, I don't mind but I just want it to be worth it. I am attaching my resistor parts list. Please help me with this. Thanks to all of you. This means a lot.
Thank you for your replies Indianajo and Kay Piranha. My apologies for responding late. Am recovering from an accident and was immobile for some time. During this time, the technician building a new board for me has come up with the parts list for the board. You were right. There is a considerable amount of Carbon Film Resistors and maybe 5 Metal Film resistors. Do I follow the exact configuration and replace them with Carbon Film or replace everything with Metal Film? What brand of resistors do you recommend? I am not very tight with budget but at the same time, do not want to buy into unnecessary expenses. Even if the resistors cost more, I don't mind but I just want it to be worth it. I am attaching my resistor parts list. Please help me with this. Thanks to all of you. This means a lot.
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Also, my bad time, all the right channel transistors have been damaged in the amplifier for a long time. The right channel transistors on the heat sink.
Transistors in Power Circuit:
NPN, MJ3247
PNP, MJ3237
NPN, DAR, MPS-A14
I am not able to find these transistors or alternates online at all. Does anyone have any suggestions on this?
Transistors in Power Circuit:
NPN, MJ3247
PNP, MJ3237
NPN, DAR, MPS-A14
I am not able to find these transistors or alternates online at all. Does anyone have any suggestions on this?
metal film resistor brands I like are in post #3.
MPSA14 is in stock newark.com $.12 each
MJ3247 MJ3237 are not in my Motorola databooks and datasheetcatalog.com doesn't know anything about them. You need to tell us what board they are on and what Q numbers.
MPSA14 is in stock newark.com $.12 each
MJ3247 MJ3237 are not in my Motorola databooks and datasheetcatalog.com doesn't know anything about them. You need to tell us what board they are on and what Q numbers.
Both the MJxxx are TO-66 style, 120Vceo, 8A and 20MHz. The MJE15028/29 pair are pretty close.
Craig
Craig
Yes, if you are made of money. $.95 to $1.44 each for 500 mw 250 v resistors at newark today. Note 250 v resistors are short, could short across after some years in a coastal salt environment. I prefer 300 v.
I usually buy the brands in post # 3 for $2 a hundred or less. You can't use 500 mw resistors for the 2 or 5 watt resistors.
I usually set the selector to in-stock, no shipments from UK, through hole, metal film, nominal resistance +-10%, wattage 600 mw to 3 w, click go, see what comes up. If one of the brands in post # 3 comes up, voltage is not too low, length is not too long, then I buy the cheapest. Often 1% resistors of slightly off EIA nominal value come up the cheapest, since newark has an end of roll. Mouser stockes Xicor, which I found always came from a country I don't respect. Digikey doesn't have sale prices on end of roll or old stock. Resistors in tape, you have to pull the tape off & clean the lead with alcohol. Worth it to me to save $1 each.
Stock in the farnell UK warehouse can buy you multiple $9 boxes as they dribble in, and sometimes a 8 week delay (in customs probably).
If you buy a lot of $.06 parts at 2 each, you may be hammered with a handling fee. I usually buy whatever quantity is $1, up to $2 for 100 if it is a value I might use again.
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Good day everyone. My new boards are getting soldered now. It was a nightmare procuring parts for them. Lots of things have changed in 40 years I guess. I'll post pictures of them after the 19th. Am very grateful for all your help and this means a lot too me. Thank you all of you.