MARANTZ 2230 power amp. PLEASE.help.
Sanity check.
You did put the mica insulators under the new output transistors, right?
You did put the mica insulators under the new output transistors, right?
jFF_Bulbo
Active Member
hello. i will work on your suggestion inmediattly. will report here in some hours
regards!
jFF_Bulbo
Active Member
71v in the board "oK", unit plugged to 120v. black terminal VTM to chassis, red to red wire that come from postive side of 4700 uF capacitor. I will check voltages on H755 from god amp.
jFF_Bulbo
Active Member
Hello AK'ers.
Well. i was in the measure moment when r771 of good channel EXPLODED in an impressive way... i was checking voltajes on h756 (a606 sub w/2n5416) an accidentally i touched emisor and the metal case with the VTM tip, then R711 set on fire.......
my readings before that short happened was:
P750, LEFT CHANNEL (THE "GOOD") VOLTAJE, DBT CONECTED . NO SMOKE ON R771.
j764-62 -----0v
j579 ----- 39.2
J761-----0.6
J760 -----39.6
J758---- 39.5
J756-----57.5
J757-----40
J755,63-----58.3
P750, RIGHT CHANNEL (THE "BAD") VOLTAJE, DBT CONECTED . NO SMOKE ON R771
j764-62 -----
j579 -----
J761-----21.8
J760 -----31
J758---- 31.3
J756-----52.8
J757-----31
J755,63-----57.6
H755, C959 SUB W/2N3440, LEFT CHANNEL, DBT CONECTED
E----- 58
C------58
B-----42
H755, C959 SUB W/2N3440, RIGHT CHANNEL, DBT CONECTED
E-----52.2
C------57.3
B-----36.7
H756, CA606 SUB W/2N5416, LEFT CHANNEL, DBT CONECTED
E----- 40
C------0.6
B-----39.4
H756, CA606 SUB W/2N5416, RIGHT CHANNEL, DBT CONECTED
E----- HERE R771 EXPLODED. END TEST.
C------0.6
B-----49
H755, C959 SUB W/2N3440, RIGHT CHANNEL, 120V PLUGGED UNIT
E----- 69
C------69
B------53
WITH 120V, C007 feeds the boards with 69v on positive (red), 0v with negative (white).
r771 after the short.
At this point, I've changed -almost- all the pieces in both boards, rectifier bridge i guees is OK because c007 feeds 69v to both boards..... the only suspect is the set of TO-3 transistors....... all of them are news, MJ15024 "ORIGINAL OEM WITH WARRANTY" I bought here in a famous electronic store in Mexico...... i bought about 15 mj15023/24 in order to have stock fore the 2235b, 2385 and the 2230 on this post.
i will delay this repair/upgrade until the new output transistor arrives.......
in a personal note, it is unveliablable about 8 mj15024 were bad... even for OEM or fakes transistors it is a high ratio.....
THANK YOU SO MUCH FOR YOUR KIND HELP,
ONCE NEW OUTPUT BE WITH ME, AND I HAVE DONE THE RECAP ANT REPLECEMENT OF TRANSISTORS, I WILL POST THE RESULT HERE.
REGARDS!!!!!!
Well. i was in the measure moment when r771 of good channel EXPLODED in an impressive way... i was checking voltajes on h756 (a606 sub w/2n5416) an accidentally i touched emisor and the metal case with the VTM tip, then R711 set on fire.......
my readings before that short happened was:
P750, LEFT CHANNEL (THE "GOOD") VOLTAJE, DBT CONECTED . NO SMOKE ON R771.
j764-62 -----0v
j579 ----- 39.2
J761-----0.6
J760 -----39.6
J758---- 39.5
J756-----57.5
J757-----40
J755,63-----58.3
P750, RIGHT CHANNEL (THE "BAD") VOLTAJE, DBT CONECTED . NO SMOKE ON R771
j764-62 -----
j579 -----
J761-----21.8
J760 -----31
J758---- 31.3
J756-----52.8
J757-----31
J755,63-----57.6
H755, C959 SUB W/2N3440, LEFT CHANNEL, DBT CONECTED
E----- 58
C------58
B-----42
H755, C959 SUB W/2N3440, RIGHT CHANNEL, DBT CONECTED
E-----52.2
C------57.3
B-----36.7
H756, CA606 SUB W/2N5416, LEFT CHANNEL, DBT CONECTED
E----- 40
C------0.6
B-----39.4
H756, CA606 SUB W/2N5416, RIGHT CHANNEL, DBT CONECTED
E----- HERE R771 EXPLODED. END TEST.
C------0.6
B-----49
H755, C959 SUB W/2N3440, RIGHT CHANNEL, 120V PLUGGED UNIT
E----- 69
C------69
B------53
WITH 120V, C007 feeds the boards with 69v on positive (red), 0v with negative (white).
r771 after the short.
At this point, I've changed -almost- all the pieces in both boards, rectifier bridge i guees is OK because c007 feeds 69v to both boards..... the only suspect is the set of TO-3 transistors....... all of them are news, MJ15024 "ORIGINAL OEM WITH WARRANTY" I bought here in a famous electronic store in Mexico...... i bought about 15 mj15023/24 in order to have stock fore the 2235b, 2385 and the 2230 on this post.
i will delay this repair/upgrade until the new output transistor arrives.......
in a personal note, it is unveliablable about 8 mj15024 were bad... even for OEM or fakes transistors it is a high ratio.....
THANK YOU SO MUCH FOR YOUR KIND HELP,
ONCE NEW OUTPUT BE WITH ME, AND I HAVE DONE THE RECAP ANT REPLECEMENT OF TRANSISTORS, I WILL POST THE RESULT HERE.
REGARDS!!!!!!
Last edited:
jFF_Bulbo
Active Member
YES SIR, NEW MICA ON ALL THE TO-3. mj15024 are now the suspect. unfortunatelly i don't have other tha change.
jFF_Bulbo
Active Member
FAKE transistors... They'll blow things every time. What's inside is likely the equivalent to a low voltage, low gain TO-92 die and shorts almost immediately.
the 024's, new with insulator
jFF_Bulbo
Active Member
a expensive bill for try to save money........ what a shame.....
jFF_Bulbo
Active Member
i have to ruin 2 P750 to learn about the fakes to-3.... i feel bad about this...
Don't feel bad, you're not the first to have experienced this. If there is a "warranty" on them, get your money back and buy from a legitimate source.
I use ON Semi MJ15024 and MJ15025 all the time. They are made in Mexico By ON Semiconductor (Motorola). The problem is if you buy them on Ebay, you are sure to get counterfeits. I buy them only from Nework or Mouser (but they aren't cheap). I have never had issue with them. In the distant past I tried purchasing some from Ebay to test, and they ALL tested way under the specified Vceo. (should be 250 volts +, but tested around 60 to 80 volts) I just threw them in the trash.
Get these. Mouser is also in Mexico. https://www.mouser.com/ProductDetail/ON-Semiconductor/MJ21194G?qs=HVbQlW5zcXVQxZkOqmVvOA==
Boy, it sure is hard to find good help nowadays, isn't it?
jFF_Bulbo
Active Member
hello everyone!!!
i have competed the 2230 recap & upgrade. new transistors installed. this is what happened:
-unit pass ok on DBT
-unit performing ok w/120v power. nothing exploded. FM noise on headphone, no speakers connected.
-BUT bias couldn´t be fixed. the best reading was 1.9 mV both channels, stable. after that, a simply touch on R765 (1k variable resistor, trimpot) and bias just climbed until 11mV ans was unestable.
-i turned off the unit. i set the r760 pot on R channel to max, and as soon as i powered the unit, r773 exploded..... (before thi, r771 was the one exploding, many times)
well. at this point, r chnnel will be re-built (again).
--a low bias like mine, 2 mV vs 5 mV on serice manual, is bad?
--the stabistor on this uniot in¿s not in touch with heatsink, close to this but not in direct contact. should it be?
as you can see, almost all the P750 board components are new: elec caps, mani resistors, trimpot, all the transsotrs are new.... and i can just fix bias to 5 mV.....
suggestions???
i have competed the 2230 recap & upgrade. new transistors installed. this is what happened:
-unit pass ok on DBT
-unit performing ok w/120v power. nothing exploded. FM noise on headphone, no speakers connected.
-BUT bias couldn´t be fixed. the best reading was 1.9 mV both channels, stable. after that, a simply touch on R765 (1k variable resistor, trimpot) and bias just climbed until 11mV ans was unestable.
-i turned off the unit. i set the r760 pot on R channel to max, and as soon as i powered the unit, r773 exploded..... (before thi, r771 was the one exploding, many times)
well. at this point, r chnnel will be re-built (again).
--a low bias like mine, 2 mV vs 5 mV on serice manual, is bad?
--the stabistor on this uniot in¿s not in touch with heatsink, close to this but not in direct contact. should it be?
as you can see, almost all the P750 board components are new: elec caps, mani resistors, trimpot, all the transsotrs are new.... and i can just fix bias to 5 mV.....
suggestions???