petehall347
the brandy coffee man
leave all outputs out of circuit and check dc offsets .. if good try headphones at low level if possible . if sound ok try new outputs .
2270 transformer testing
- Thread starter mistermojo
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- 2270 fuse blow marantz transformer
mistermojo
New Member
Do the headphones have their own amp? I hadn't noticed. This is a good suggestion. I've been aware that I need to check my DC offsets, but I know neither what they are or how to check. I'll have to start RTFM! Thanks
petehall347
the brandy coffee man
basically if you remove output transistors you are left with the outputs driver transistors at lower power output .. dc offset is measured at the speaker outputs and is indicative as to if the rest of the circuits are working ok . good clean low level music on headphones sort of confirms everything should be ok Barr service adjustments after replacing outputs . never any guarantees though
mistermojo
New Member
Hey everyone,
Last night I got it all back together and working perfectly. Thanks for all the help, it would have taken a lot longer without it.
Turns out that the only problem was the one fried output transistor. I replaced all four of them with the OnSemi units. After passing the DBT check, I set my DC offsets, and set power supply voltage. I couldn't get my DVM attached to the pins for setting the Idle current. I need some smaller clips for it. Might be time to upgrade from my Craftsman to a Fluke or something.
It sounds so good with all the new caps! I've only done P800 and the P750s. I think I'll tackle the P400 next, but I'm going to enjoy the way it sounds now for a little while so I can use my kitchen table for its intended purpose.
Thanks again to Pete, Steven, and rBuckner for your help. So happy to have it up and running again.
Last night I got it all back together and working perfectly. Thanks for all the help, it would have taken a lot longer without it.
Turns out that the only problem was the one fried output transistor. I replaced all four of them with the OnSemi units. After passing the DBT check, I set my DC offsets, and set power supply voltage. I couldn't get my DVM attached to the pins for setting the Idle current. I need some smaller clips for it. Might be time to upgrade from my Craftsman to a Fluke or something.
It sounds so good with all the new caps! I've only done P800 and the P750s. I think I'll tackle the P400 next, but I'm going to enjoy the way it sounds now for a little while so I can use my kitchen table for its intended purpose.
Thanks again to Pete, Steven, and rBuckner for your help. So happy to have it up and running again.
Steven Tate
CEO Flat Forehead Soc.
Well done! You really need to get the idle current set. AK member Echowars has a great thread that tells the equipment one needs if he wants to get into this hobby. Point #4 about multimeters and leads tells you exactly the mini-grabbers you need. Order them (red and black) from Digikey and get the idle current set. The service manual has the wrong info for 2270's higher than serial number 3900. Use the mini-grabbers on J754 and J760. Set R763 to 10mV. The reading will start low and slowly climb over 30 minutes. Keep adjusting so the setting doesn't rise too high, and do that until it pretty much settles at 10mV, and of course, do it for both amps.
Steve
http://audiokarma.org/forums/index....udio-gear-eh-heres-the-tools-you-need.333423/
Steve
http://audiokarma.org/forums/index....udio-gear-eh-heres-the-tools-you-need.333423/
mistermojo
New Member
Steven,
Thanks for that info. It hadn't occurred to me that I could replace the leads. I've thought for years that this Craftsman DVM I have doesn't work right, but after this project I'm pretty sure that I just wasn't using it correctly. When I get home this eve I'll see if those leads will fit. I suspect they will.
My 2270 is a later one from '79, so good to know these discrepancies from the manual. Cheers!
-Tony
Thanks for that info. It hadn't occurred to me that I could replace the leads. I've thought for years that this Craftsman DVM I have doesn't work right, but after this project I'm pretty sure that I just wasn't using it correctly. When I get home this eve I'll see if those leads will fit. I suspect they will.
My 2270 is a later one from '79, so good to know these discrepancies from the manual. Cheers!
-Tony
deedawson
New Member
Glad to hear you got it figured out. I had been following your post as I am just getting started out just as you and felt that I had a transformer issue. Just as yours, I think I have a something else other than the trans. Good job with the group troubleshooting. You are giving me hope on getting my 4300 operational again!
mistermojo
New Member
dee, I thought it was funny that everyone blew past my "how to test transformer" question and made suggestions that were far more likely to get me to the solution. Start by disconnecting all the secondary wires from the transformer and see if you can get it to fire up. The re-attach them one at a time, starting with the lights, and see which section causes you trouble, then you'll know where to focus your efforts. Good luck!