Reeves C225 developed a problem

rockbobmel · September 21, 2018, 03:34:55 PM

I gigged 4 times with the amp and no problems. Last gig after 2 songs in, I got a nasty crackling when I played hard. I doesn't sound like a typical distortion, more like a blown speaker. It is not the speaker, any of the preamp tubes ( I swapped them out 1 at a time). Acts the same with active or passive, 3 DIFFERENT CABS, 4 & 8 Ohm. I brought it to the local tube guru and when he tested it, the problem did not occur with him. ( I think he has only guitar stuff).Power tubes are OK. Resistors checked OK.

I'm at a real loss here. So discouraged!

amptech · September 22, 2018, 01:58:21 AM

Did he measure the power tubes? Leak/shorts? Even tubes with normal gm/pc can have loose electrodes developed over time.

Also, did he test with a dummy or a speaker? Loose electrode related problems obviously more likely to occur on top of a speaker driven hard.

That said, it can be so many things. I've had a number of recent Blackstar amps in, with problem like you described. This is related to a bad coupling cap (the very type, not how it is supposed to measure) between plate and grid cct in the preamp.

Also, power supply issues. Loose connections between sockets and pcb, bad pins i socket.... list goes on:-)

Soundclips?

Basvarken · September 22, 2018, 06:19:20 AM

Is the speaker cord /connection okay?
I've had similar problem with a bad jack input on one of the cabs. Been using Speakon connectors ever since.

rockbobmel · September 22, 2018, 11:27:11 AM

Link to video.

Compared to my Sunn 2000S

4stringer77 · September 22, 2018, 11:52:43 AM

Here's a solution. Chuck the Reeves off a cliff, then buy another Sunn. I have a 2000s if you want to make an offer PM me.

rockbobmel · September 22, 2018, 11:56:30 AM

If I do, The amp will be playing obnoxiously loud and I'll set it ablaze! It won't be out of sight where I won't see it......

Thanks for the offer on the Sunn.

amptech · September 23, 2018, 01:14:22 AM

Quote from: Basvarken on September 22, 2018, 06:19:20 AM
Is the speaker cord /connection okay?
I've had similar problem with a bad jack input on one of the cabs. Been using Speakon connectors ever since.

Checking speaker cable/jacks is vital, but I can't see that switching to Speakon can solve anything.
Looking at repairs where the speaker plugs has been the problem, Speakon issues is a lot more common.
I must add to this that often it's just the sheer size of the plug and cable and how they are connected to a thin chassis material or PCB, but also loose components in the plugs and compatibility problems between manufacturers.

Psycho Bass Guy · September 23, 2018, 07:01:15 AM

Quote from: amptech on September 23, 2018, 01:14:22 AM
Checking speaker cable/jacks is vital, but I can't see that switching to Speakon can solve anything.
Looking at repairs where the speaker plugs has been the problem, Speakon issues is a lot more common.
I must add to this that often it's just the sheer size of the plug and cable and how they are connected to a thin chassis material or PCB, but also loose components in the plugs and compatibility problems between manufacturers.

+1000

Years ago, some genius started talking about how speakon plugs were better for everything and the bass community ate it up like crazy. About the only benefit is the fact that it locks. The actual contact surface for current transfer isn't much bigger than a normal t/s phono jack and as you mentioned, compatibility issues are a much larger problem between nonstandard sizes and plug configuration than a 1/4 plug popping out.

That said, I agree that whatever is wrong with the amp is in the stage coupling. Something in the power section, like a shorted OT causing that noise, would produce a much larger "whump" and fart.

Basvarken · September 23, 2018, 09:16:12 AM

I had a cabinet with a regular jack input. And it was too wide. The jackplug did not make a reliable contact. It took me quite a while to find the problem. First suspected the amp. Then the speakers.
So it turned out to be a wobbly jack input. The speakon clicks secured to the cabinet. There ain't no way that is going to shake loose, whenever I hit a low note.

Glad I replaced the jack inputs for speak-on.

rockbobmel · September 23, 2018, 09:32:31 AM

This is the actual inside of my amp. The 1/4 jacks are the top right. I'll get in there with a Q-tip and some deoxit. Please note, this started mid song, after gigging 4 times without a hiccup.

rockbobmel · September 23, 2018, 10:21:08 AM

The 2 x 1/4" speaker jacks made no difference after deoxit. I fiddled with the tone controls and the only improvement I could notice was channel volume almost max and master at 2ish. I agree, it is looking like the output stage.

rockbobmel · September 24, 2018, 01:06:04 PM

I got a reply from Bill at Reeves. He said to check the preamp resistors and caps. He had a 400 with the same issue. My tech was only looking at the power amp section.

doombass · September 24, 2018, 02:46:30 PM

That means that Bill, Amptech and PBG have the same opinion. Should be a quite cheap fix then.

rockbobmel · September 24, 2018, 05:45:30 PM

Well, I needed some knowledge to bring to my tech. I really like him, but I think he picks just the low hanging fruit first. He agreed that When he gets done, I should bring my cab and play my style (hard). I told him that "sure, if I was a light handed player, I could live with it" but this was an amp that plays the way I like and after 4 gigs, it started acting up on the second song. So it's not "me", it's the amp.

I told him that if he wants to take another swing at it, I want it remedied, no matter what.

PS, There is only one other amp tech in the area and he didn't return my call, so I really want this to work out with my current(no pun) one.

doombass · September 25, 2018, 09:45:56 AM

If your tech uses a signal generator and scope there's a good chance he'll find the exact problem area and component. If he's more of a 'shoot-from-the-hip'-guy he will probably replace coupling caps between stages and if that does'nt do it all resistors. Hope you get an easy fix.