Reeves C225 developed a problem

Granny Gremlin · October 09, 2018, 05:20:31 PM

I had a similar thing with my 70s Sunn when I got it. Tech couldn't figure it out or even hear it .

Turns out you need ed to use a bass and turn it up to hear it. Hairline crack through one of the power tube's screen resistors (carbon) that would vibrate open on a heavy transient. The leads acted like a spring t keep the 2 halves together in between transients. Screen resistors are usually metal or wirewound but Sunn left these as carbons,I forget exactly why, but they act as safetey fuses - they go vs the tube or OT.

Open up the amp and poke each resistor around the tubes with a (wood/plastic) chopstick to see if they separate; you can't even see it (I found it by accident poking around like that). Carbons only, metal films, wirewounds or other types should not do this. The amp is a bit too new for the carbons to wear out to heat exposure but stuff happens.

Since Reeves said so and because your amp in the vid seems to do it easier them mine I wouold start with the resistors around the preamp tubes vs power like mine, but check em all.

rockbobmel · October 25, 2018, 02:21:29 PM

I just got the amp back from Bill Jansen (Reeves) and it's FIXED!!! I was so worried it was one of those "can't find it" situations. Apparently, it was a bad power tube socket.

Rob · October 25, 2018, 06:29:32 PM

That was the best you could hope for!

rockbobmel · November 04, 2018, 01:20:12 PM

Embarrassingly enough, I was able to recreate the problem again. It was when both NORMAL AND BRIGHT channels were over 12 noon, even when I was not using a Y cord. Something about the 2 gains at the same time. When I used NORMAL or BRIGHT on their own, with the other input volume low or off, there was no issue. I probably wasted everyone's time AND my money blaming the amp when it was probably not even the tube socket at fault. It never occurred to me,(and I don't recall) the settings I used on the live gigs BEFORE when the "issue" occurred.
So in some way, I get resolution, knowing it was not the amp's (or Reeves') fault, nor was it mine, aside of missing the "conditions" that caused the issue.
I didn't get back to Bill with this because I discovered it just a few days ago and I felt that I bothered him enough.
Lesson Learned!!
BTW, this amp completely blows my mind- how good it sounds AND feels!

Granny Gremlin · November 05, 2018, 10:23:28 AM

Wait, using both inputs should be possible.

rockbobmel · November 05, 2018, 02:37:19 PM

Yes, I agree. I am pretty sure V1 shares the input from the Normal AND Bright channel --which in turn may have something to do with it.

Granny Gremlin · November 06, 2018, 11:55:46 AM

If there are 2 seperate gain controls as I think you said up there somewhere then it should be dual channel (the 2 jacks feed separate gain stages) not dual input. But even if not (dual input to same gain stage) it still should work - do it on my Sunn all the time. Classic Fenders work this way too.

... yeah, dual channel:

in the schem V1 is a dual triode so normal feeds V1.a and brilliant feeds V1.b. You should be able to use both inputs and crank them any way you like.

clankenstein · November 06, 2018, 01:17:27 PM

Could it be that those switching jacks on the inputs need a squirt of deoxit?

doombass · November 06, 2018, 04:33:52 PM

Or possibly the V1 tube? You could try to swap it with V2.

rockbobmel · November 06, 2018, 05:59:56 PM

No on Q 1. Did that on Q 2.

amptech · November 06, 2018, 11:37:35 PM

I have to stress that it should be simple enough as long as you can create a signal that leads to the malfunction.

I like to set up a tone generator to 'replicate' the notes that makes the amp iffy. If you can create a sine and have the amp malfunction, scope until you find it.

Did you (or they) rule out leaky coupling caps? I'd check the point where the mixer resistors meet after V1 (if the schem that Granny posted is the same as your amp). If the sine looks bad there then you have found the problem more or less. If one of the 22N caps are bad they'd make a sound like you described. If it's not the case, just probe until you find it. I just assume that the tubes have no leakage and are fully tested.

rockbobmel · November 11, 2018, 06:29:06 AM

I am using the amp this Friday with 2 x Aguilar GS112s. We'll see if I can still use the Y cord. I am pretty sure it'll be OK as long as the normal channel is kept below 9:00