Hello, I am a newbie to this site. Tim Tengberg, the owner of HiFi Haven in Whittier, CA suggested I inquire on this site for someone to repair my Marantz 250…so here I am.
I bought this amp six years ago. It was working. I took it to a tech in San Diego. He replaced the left channel output transistors with sets of Toshiba. The unit was working but soon something else started to fail. I took it to George Meyer AV in Los Angeles. They did more extensive repairs by replacing additional capacitors. But it wasn’t totally “recapped.”
Last year I found a guy in New Jersey who had recapped a Marantz 3200 preamp and a Marantz 140 power amp. Since I had both, I sent mine to him and he gave them a thorough service. They came back sounding better than they did in 1974!
So I decided to send my Marantz 250 to him for a total recap service. He replaced the main filter caps with 22000uf Nichicon NT. He recapped the amp board by removing the cheap no brand caps George Meyer had put in. He rebuilt the meter board. Basically, he did a nearly complete recap…but he left the Toshiba and original Motorola output transistors because they seemed to be fine to him. i felt it was a mistake…but he said that setting BIAS might be more difficult if he replaced them.
I got the amplifier back and it was working fine for about 10 hours of play time. Then one night i turned it off…and the next day it wouldn’t work — the protection relay would not kick-in.
At first he thought it was the m=new, modified relay he put in…so he send me a new one. Since he installed a socket, it was plug and play. I plugged in the new relay. Didn’t work. That wasn’t the problem.
Next he thought it might be the bridge rectifier. But I tested and that wasn’t it.
So we removed the right channel (original Motorola) output transistors. But then relay didn’t kick-in. I then removed the left channel (Toshiba) output transitions — and the relay kicked-in!
I tested the output transistors, and the top two (PPN, I think) were bad.
So…the long and short of this story is the output transistors in the left channel have gone out again. I could buy matched sets of Onsemi replacements — but those would likely just fail in time unless I can discover what in the left channel board is Actually causing the problem with the output transistors going out. Maybe its some transistors or a diode. I didn’t know. And I don’t have the skill and knowledge or equipment to figure it out.
I didn’t send it back to the tech in New Jersey because he doesn’t have time to do it now and its yet another $250 roundtrip shipping expense. I was hoping to find someone qualified and experienced closer to me — possibly in Southern California.
So if anyone has a recommendation or referral — I would greatly appreciate it.
And yes, I could sell it for peanuts, or forget about it…but it seems its just one service away from greatness! Help me save this relic of an earlier age in audio!
Thank you for reading and responding.
So…I am hoping to find someone
