amp help needed

[jackson111]

ok guys need some help diagnosing a problem. finally got my black star re-tubed sounds different kinda flat, well anyway i have biased the amp correctly and everything, know i have noticed 2 things #1 my plate voltage is different between my 2 el34 tubes, they used to be identical, but know one plate reads 512vdc the other bounces between 513 and 514vdc, #2 when i use the amp it will occasionally have a loud pop, still keeps playing and it doesnt happen all the time. to give you an idea we played about 2 hours straight last night and it popped twice. like i said never dies the sound doesnt dimenish, the volume stays consistant just scares the crap ot of me cause its rather loud. anybody have any suggestions?

 

[VanDerchuck]

Re: amp help needed

Well. It could be a few things. Where did you set the bias? And did it have any issues before? And have you tried putting the old tubes back in to see if that changed anything?

 

[jackson111]

Re: amp help needed

ok according to blackstar you have to bias the power tubes together not one at a time, they recommend 50mv, i sit it there but the amp sounded horrible on the distortion channel, so i wound up uping it to 57mv. i had owned the amp for a little more then a year when the amp made a poping sound and then died during a show. i took it back to where i got it, they said the power tubes tested bad, one had short, the other got weaker the longer it ran. they re-tubed it and it sounded great but very loud, then the amp lost most of it volume after about 2 months and when i would play it would sound almost like a leslie or as if i would strike a chord and very quickly turn my volume pot back and forth on my guitar. i eventually found that when they re-tubed it they used (3) ecc83 tubes as the preamp tubes when it actually was supposed to be (2)ecc83 and (1)ecc82 this is the phase inverter tube. i ordered a new ecc82 and it started back up fine, the volume level had returned back down like it was when the amp was new, but like and it was great for a few weeks before the popping started, thats when i noticed the plate voltage beign different

 

[VanDerchuck]

Re: amp help needed

Plate voltage can be relative to the current. So, yes it's very possible to have different plate voltages. And at around 500 vdc you should be around 33 or 34ma for a class ab amp and 42-43ma for class a. I'm not familiar with your amp. And from my knowledge you could be biased hot. I'm not a working tech so take my opinion how you like, but 51ma might be way off. If that's the case, then a simple rebias might help. What kind of tubes are you using? And have you cooked the paint on them? If you have then you know its to hot. If you have a link to the schematic it might help us figure it out faster. The volume of the popping is a tell tale sign it's after the master volume. Probably post PI. It could be just the power tubes.

 

[Dennis Hrapeck]

Re: amp help needed

The pop sounds like a tube socket that's went bad

 

[VanDerchuck]

Re: amp help needed

Jackson111: from the little reading I've done 50ma seems to be a common set point. Not sure why this is, but maybe it's an unfamiliar set up. That doesn't explain the popping. It could be a bunch of things. I had a similar experience with a JCM800 build I did a couple years back. At 100 watts, man that was a loud scary pop. So I understand the concern. There is a Blackstar Amps forum. I'd look there. Maybe someone who has more insight can help you out. Whether it's a common problem, bad cap, or as previously suggested, a bad socket. Good luck.

 

[jackson111]

Re: amp help needed

yeah I have tried the blackstar forum unfortunately the forum seems dead, I have been waiting on an answer for 2 weeks. I did get an answer from blackstar that told me how to bias. they told me to set it to 50mv but they also mentioned that was based on a plate voltage between 430 to 480 vdc. that's why I mentioned the plate voltage being higher. when the amp was retubed the only thing the store had were mesa boogie tubes. I have been told they are good tubes, but so far I don't like the tone the clean sounds deep beautiful and full bodied but when I go to channel 2 the overdrive sounds fuzzy similar to a fuzz face (which I have never cared for) it used to have an overdrive similar to a marshall amp.

 

[jackson111]

Re: amp help needed

ok I have never had to get service from a professional tech but I have found one about an hour from my house in Charlottesville Virginia. they are supposed to be very good they are called universal electronics repair and they are an official blackstar repair center. I called them and their backlog is running about 6 weeks. they guy I spoke with Roger Pinto (who actually is the owner) told me he could give me same day service for a 40.00 charge, and that it would probably be at max 2 or 3 hours to diagnose and repair the amp. they charge 50 an hour and as long as I get them to do the repair they will waive the diagnostic fee. plus he told me I would have a 1 year warranty on the amp after the repair. has anyone ever heard or had their amps serviced here. the owner seemed very nice and very informed by questions he asked me. he told me he could not give me an estimate over the phone but that it didn't sound too serious considering the amp still worked, but he did tell me he would give me a guaranteed estimate before they did any work. he also told me when they diagnose the amp they go through everything and don't just stop at the first problem they find.

 

[VanDerchuck]

Re: amp help needed

I'm not sure about the prices, every shop is different. But it's good that you found someplace you're comfortable with. If they do a great job, then you'll probably be a customer for life. That's what great shops are working for. Good luck and let us know what it was and how it turned out.

 

[jackson111]

Re: amp help needed

ok I feel like a complete idiot. I found a local technician named roger pinto at universal electronics in Charlottesville Virginia and I took my amp to him today. he used an oscilloscope to check out and couldn't find a thing wrong with it. he played the amp for almost 3 hours an he couldn't get it to fail. then he called me and asked if I use effects. I said yes I run a wah in front of the amp and in my effects loop I runa mxr carbon copy, tc corona chorus, and finally an electro harmonincs lpb-1 boost pedal. he asked if the amp ever messed up without the effects. I really didn't know what to say. he told me to play the amp and slowly install the effects one at a tie and that he thought it was probably a bad cable or it could be a bad effect. good news is he only charged me 50.00 for the service which 40..0 of that was his expedite fee, and he gave me a 3 month warranty that if the amp did die he would wave the expedite fee and would credit me 50.00 towards any repairs that need to be made. I could look at this and get upset, but the one good thing is that I found a trust worthy amp tech.

 

[VanDerchuck]

Re: amp help needed

It's probably one of them in the effects loop. After the volume knob. I never would've thought of that. Maybe when you test them, if you haven't already, try them straight into the amp so you don't get the full volume pop.

 

[jackson111]

Re: amp help needed

yeah I didn't think of it either, like I said I kinda got upset cause I should have tired that first, but on the up side he seemed very honest and knowledgable. I haven't tried them yet but I did run it at practice last night and it was killer. he did suggest possible changing speakers and getting a nice power conditioner for when I play out. he explained the power conditioner keeps the power feeding the amp clean he told me an inconsistent power supply can drive an amp nuts. as far as the speakers my amp has celestion 70/80 speakers. he told me that is a low end speaker from celestion. he recommended if I want to stay with celestion to try the the green back or vintage 30. he even suggested if I was on a budget to just get on new speaker and mix it with the remaining 70/80, and I may like that.

 

[Agileguy_101]

Re: amp help needed

Yeah I can tell you from personal experience that you don't know how bad the Seventy/80 is until you replace it. I don't have any experience with your amp, but I had a Crate V32 (4xEL84, 2 channel head) and a matching combo that came with two of those speakers. I replaced one and it was a night/day difference. If you're on a budget I'd actually recommend you get two Eminence speakers instead of one Celestion - I've used them for a while now and they sound absolutely fantastic. I've found them new for $75 (depending on the model).

 

[rumy22]

Re: amp help needed

ok I feel like a complete idiot. I found a local technician named roger pinto at universal electronics in Charlottesville Virginia and I took my amp to him today. he used an oscilloscope to check out and couldn't find a thing wrong with it. he played the amp for almost 3 hours an he couldn't get it to fail. then he called me and asked if I use effects. I said yes I run a wah in front of the amp and in my effects loop I runa mxr carbon copy, tc corona chorus, and finally an electro harmonincs lpb-1 boost pedal. he asked if the amp ever messed up without the effects. I really didn't know what to say. he told me to play the amp and slowly install the effects one at a tie and that he thought it was probably a bad cable or it could be a bad effect. good news is he only charged me 50.00 for the service which 40..0 of that was his expedite fee, and he gave me a 3 month warranty that if the amp did die he would wave the expedite fee and would credit me 50.00 towards any repairs that need to be made. I could look at this and get upset, but the one good thing is that I found a trust worthy amp tech.

I was going to tell you to test everything one by one... But I think you had to hear it in person. Always try to simplify signal sound problems. If something is awry in my rig, i strip back to guitar, amp and cable. If all is good, I slowly add gear.

In uour case, i sense maybe one lf the delays is acting up.

 

[jackson111]

Re: amp help needed

ok cool I was wondering about the eminence speakers and I also found a company called warehouse guitar speakers. I got 2 kids and I'm on a tight budget. so I'm trying to stay around 80.00 if I can and I will switch them out 1 at a time. never switched speakers so any help would be great. someone recommended a red coat but when I look at the eminence site looks like they got a ton of redcoats. also I have heard the patriot was a good speaker. I mainly play classic , southern bluesy rock

 

[Agileguy_101]

Re: amp help needed

I'd recommend a Eminence Texas Heat for your first speaker and either a Swamp Thang or Cannabis Rex (probably the former) for the second one. Should be a great match.