The Last Bass Outpost
Gear Discussion Forums => Bass Amps & Effects => Topic started by: rockbobmel on September 21, 2018, 02:34:55 PM
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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!
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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?
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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.
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Link to video.
https://www.youtube.com/watch?v=wV2BlXT7Wro
Compared to my Sunn 2000S
https://www.youtube.com/watch?v=w5xX5Y8FzT8
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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That means that Bill, Amptech and PBG have the same opinion. Should be a quite cheap fix then.
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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.
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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.
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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.
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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. 8)
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That was the best you could hope for!
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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!
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Wait, using both inputs should be possible.
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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.
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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:
(https://hiwatt.org/Schematics/DR_Pre4Input_v1a.gif)
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.
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Could it be that those switching jacks on the inputs need a squirt of deoxit?
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Or possibly the V1 tube? You could try to swap it with V2.
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No on Q 1. Did that on Q 2.
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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.
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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