Wow AA sure has some detailed asylum categories - never been in this one before!I got a heavily upgraded Ming DA MC7R that has malfunctioned from day one. It sounds great when first turned on, but after about 15 minutes cuts in and out while sputtering loudly - very loudly.
Attached is a pic - in case anyone can spot components known for high failure rates.
I will take it to a shop locally as I have no technical skills at all - this guy works on tube and vintage tube gear so they say, I'm sure he has to get running a lot of their vintage trade-ins. If I can gather some suggestions here though, it probably can't hurt.
This was a somewhat expensive upgrade and until it sputters and scares me out of my chair, it actually sounds pretty good even with the Chinese tubes. Yes, I have swapped the entire set of tubes with my other non-upgraded MC7R. Sadly, that wasn't it.
What could start to fail as it warms up - 15 minutes? The transformers weren't even getting warm at that point...
PS this is the so-called "extreme" mod from RAM - click link for details
Further update - switch rectifier tubes, still happens. Timed it, takes 20 minutes to start crackling. But, so far - it happens in episodes - crackles for 10-15 seconds, then stops. I expect episodes will get closer together - am monitoring...
Further update - damn this thing sounds good. 30 minutes play time, two sputtering episodes. When not sputtering, seems perfect.
Hmmm... One hour of listening - still only two outbursts of popping, but at all times there is a low level static on one channel. Not enough to interfere with listening, but easily heard when no music. Static at same level when volume is at zero.
Ouch - major outburst at 1 hour 10 mins, popping in/out rapidly - sounded like a machine gun for a good 15 seconds. I think it did so even when source selector was changed but will have to verify that "next time".
Ok - another outburst of machine gun fire for 20 seconds at 1 hour 30 minutes of listening - confirmed, popping / machine gun fire continues even when source selector is changed. That can't be good.
Thanks in advance
Edits: 08/08/12 08/08/12 08/08/12 08/08/12 08/08/12 08/08/12 08/08/12
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Topic - Possible causes of tube preamp sputtering when warms up - with pick - longtimequadowner 15:00:27 08/08/12 (6)
- Thanks guys - longtimequadowner 13:24:43 08/09/12 (0)
- RE: Possible causes of tube preamp sputtering when warms up - with pick - DAK 21:17:39 08/08/12 (0)
- Here's a pic of the stock unit - longtimequadowner 18:07:51 08/08/12 (0)
- RE: Possible causes - grhughes 17:15:46 08/08/12 (0)
- You have a bad resistor. Don't use this until it is fixed. - Chris O 17:12:57 08/08/12 (1)
- RE: You have a bad resistor. Don't use this until it is fixed. - bwb 06:49:40 08/09/12 (0)