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Carver TFM-35 transistor replacement

Posted: Fri Jan 18, 2013 11:36 am
by OOsemka
Hello Carver Forum,

This is my first post here an I was hoping someone could help me out.
I have a non-functioning Carver TFM-35. I have noticed on the PCB board few burned ressistors and transistors. One of the transistors exploded (q216) badly and I am looking for replacement. The original transistor is 2SC2240 with following specs:
Collector-base voltage VCBO 120
Collector-emitter voltage VCEO 120
Emitter-base voltage VEBO 5
Collector current IC 100 mA
Base current IB 20 mA
Collector power dissipation PC 300 mW
Junction temperature Tj 125 °C

These are no longer in production and I was going to replace it with KSC1845 that has the same pinouts and very close specs. The only difference is IC and IB. Here they are:
Collector-base voltage VCBO 120
Collector-emitter voltage VCEO 120
Emitter-base voltage VEBO 5
Collector current IC 50 mA
IB Base Current 10 mA
PC Collector Power Dissipation 500 mW
TJ Junction Temperature 150 °C

Would it be ok, to use KSC1845 here as a replacement even though they are not identical?

There is also ztx694B with the different pinout but more capable specs (in terms of IC):
Collector-Base Voltage VCBO 120
Collector-Emitter Voltage VCEO 120 V
Emitter-Base Voltage VEBO 5 V
Icm 1A
Ic 0.5 A
Practical Power Dissipation* Ptotp 1.5 W

It's also more expensive and the pin-outs needs to be messed up with.

Please advise. [-o<
Chris

Re: Carver TFM-35 transistor replacement

Posted: Fri Jan 18, 2013 12:52 pm
by hewlew1
Hello and welcome to the forum. MCM Electronics suggests 2SC2547 as a suitable replacement for the original . The cost is 6 cents each or 5 cents each in quanitys over 25 pieces.

Re: Carver TFM-35 transistor replacement

Posted: Fri Jan 18, 2013 2:41 pm
by OOsemka
I have never heard of MCM Electronics before. I usually order parts from Mouser or Digi-Key. However I love how they find a suitable replacement. Thank you.
I also ordered the other 2 mentioned by me in first post, since I was unable to find anything better before you pointed out to MCM Electronics. I wonder if I could still use one of them instead.

Re: Carver TFM-35 transistor replacement

Posted: Fri Jan 18, 2013 8:53 pm
by hewlew1
ZTX694B would be more suited as I would rather have something rated for a little more current rather than less.

Re: Carver TFM-35 transistor replacement

Posted: Sat Jan 19, 2013 5:33 am
by Magic_Physicist
Yes you should be able to trust MCM and they have been around for a long time.

I used to get my parts and tools from them way back in the 80's and 90's for my company (ICM Electronics)

In fact I was just thinking about them because my VOM I got from them almost 30 years ago finally needs to be replaced and I see they still are pretty cheap.


Re: Carver TFM-35 transistor replacement

Posted: Sun Jan 20, 2013 2:43 pm
by OOsemka
Thank you for all the help.

Re: Carver TFM-35 transistor replacement

Posted: Sun Jan 20, 2013 5:10 pm
by hewlew1
No problem . Keep us posted on your progress.

Re: Carver TFM-35 transistor replacement

Posted: Mon Jan 21, 2013 2:16 pm
by OOsemka
Thank you .. I got all the parts delivered. Unfortunately just caught a flu and I am unable to work on the amp. I'll post as soon as I get some results.

Re: Carver TFM-35 transistor replacement

Posted: Sat Feb 02, 2013 4:15 pm
by OOsemka
Unfortunately after replacing 2 transistors (q216, q218) and 2 resistors (R244, R246) and all the caps, I have plugged it in to the power and got a sparks and smoke from exact the same area on the PCB (q216, q218) and (R244, R246).

There must be some other component that is causing this failure. It seem to be only on 1 side. I am getting little frustrated. Can anyone give me some clues what else should I be checking ?

Re: Carver TFM-35 transistor replacement

Posted: Wed Feb 06, 2013 8:11 pm
by angelod307
ok. you need to go check the bank account and if it agrees with you, you then send the amp to tom at vintage hifi. if your on the west coast, then rolland might better. there is an entire procedure that you can go through using the 1.0 service manual as a rule of thumb to go by and the carversite members as quides to the tougher questions. otherwise send it to me, and i will pick at it in my very rare spare time with no promice of i got it. cheers and welcome.

Re: Carver TFM-35 transistor replacement

Posted: Mon Feb 11, 2013 11:11 am
by OOsemka
Thank you for your comments.

I intendent to send it out to service center originally, but then after sending emails to few places around (NY State) and not getting any response, I decided to just figure it out myself. I printed out service manual and attempted to replace components that were burned out. I also replaced all the capacitors. I am new to soldering and electronics in general. However I do have computer degree (software) and I was hoping to get this as a fun project to learn. Right now, it's not so much about the money, but learning experience for me. I probably need to dig deeper in service manual. Was hoping to find someone with similar problems and get some clues from this forum on what should I focus on most.
Thanks for suggesting Vintage Hi FI place. I'll definetly give them a call in case I can't figure out anything else.

Re: Carver TFM-35 transistor replacement

Posted: Mon Feb 11, 2013 9:12 pm
by angelod307
OOsemka wrote:Thank you for your comments.

I intendent to send it out to service center originally, but then after sending emails to few places around (NY State) and not getting any response, I decided to just figure it out myself. I printed out service manual and attempted to replace components that were burned out. I also replaced all the capacitors. I am new to soldering and electronics in general. However I do have computer degree (software) and I was hoping to get this as a fun project to learn. Right now, it's not so much about the money, but learning experience for me. I probably need to dig deeper in service manual. Was hoping to find someone with similar problems and get some clues from this forum on what should I focus on most.
Thanks for suggesting Vintage Hi FI place. I'll definetly give them a call in case I can't figure out anything else.

Hello, you have meet that person, me. Lol . I have 5 Tfm35's and replaced all caps as well. I had one amp thought that just kept kicking my butt. Replace this work for a long while then smoke. Once twice. Then I said, I will swap out all components . Even worse mistake as somehow I got a transistor backwards here and there Tom at vintage hifi told me. So now I have a 55 that I will peek at as it has an issue even thought it worked when i stopped using it. i can say it will most likely go to Tom as I must have done some wrong there as well. Or not. Either way, I love the amp, so I will not try to be a tech beyond my reach. Toms shop is the carver shop for all intense purposes.

Re: Carver TFM-35 transistor replacement

Posted: Fri Jul 19, 2013 3:44 pm
by OOsemka
Just the FYI for the forum members.

I have sent my amp at the end of February to Vintage HiFi and that's the last time I have seen it.
I have been calling and sending email to the shop and first I got some answers they have been really busy and were unable to look at it yet. Now, I get no responses neither by email nor phone calls.
I really hope that I can still get it back :-( . Not sure what to do.

Re: Carver TFM-35 transistor replacement

Posted: Fri Jul 19, 2013 8:06 pm
by hewlew1
It is best to call tom at Vintage HiFi on a weekend during the evening . I do know that he is backed up as far as repairs. He had my Sunfire for 6 months so dont worry he will get to it and it will be as good as new when he is done.

Re: Carver TFM-35 transistor replacement

Posted: Fri Jul 19, 2013 8:23 pm
by BrianT
hewlew1 wrote: He had my Sunfire for 6 months so dont worry he will get to it and it will be as good as new when he is done.
Harry

I agree, as good as new if not little better.

Brian