Hi Guys,
I have a 75 pro reverb 45 watt model. I took it to a tech and had it BF'd and NOS tubes installed. When I got it back I had all sorts of problems so I took it back to that tech a total of 4 times and everytime the problems got worse . I finally took it to a different tech and got all the issues worked out. He said a few things were done wrong . Overall , the amp is working and sounding great.
I just have a few questions and don't want to bother the new tech because he's a bit tempermental...Thats why I didnt take it to him the first time.
So far all mods are : bias supply caps, filter and electrolytic caps, MV removed, hum balance removed, added adjustable bias and reverb and tremolo on both channels. I used new tung sol 12ax7's, jan phillips 12at7's, GT 6l6 GE 's and a sovtec 5u4G.
1. My normal channel is much darker than the vibrato channel. I switched tubes and its the same. I had to put the treble on 8 or 9 to have it where 4 is on the other channel. Is this normal?
2. Rarely there is a weird sound coming thru the amp that sounds like someone it drilling in the other room. Parasitic oscilation? I switched the tubes and it still does it but it only does it maybe once the whole time Im playing thru it . I don't even know how this could be diagnosed or fixed.
3. The first tech broke my gz34 and put in a 5u4. thats in there now. Should I leave it or get another gz34? if I do I'll need to buy a bias meter or pay a tech to do it.
4. the only other thing is the signal caps. They are the blue kind whatever those are. Are those considered to be a good sounding cap? They aren't the brown ones I hear bad things about. If I would get a lot better sound replacing those which ones in particular should I do? I could do this myself.
Thats about all the gremlins though there were about 10 things wrong when the first tech messed it up(it worked perfectly before he screwed with it).
What sucks is I paid the first guy $180 to screw it up (but that included spragues and all parts) and the last guy $140 so I'm approaching the point of "why didn't I just buy a BF and be done with it"
Thanks
Shane
got my pro reverb back from the shop. a few questions:
Moderators: pompeiisneaks, Colossal
Re: got my pro reverb back from the shop. a few questions:
Gives a whole new meaning to "BF'd it", doesn't it? 
Regarding your dark/bright normal/vibrato channel issue: Are the bright caps switched or hardwired? The coupling caps after the second stage in the 165 circuit are different for the two channels - the Normal channel can be voiced brighter to match the Vibrato channel if you like.
Regarding your dark/bright normal/vibrato channel issue: Are the bright caps switched or hardwired? The coupling caps after the second stage in the 165 circuit are different for the two channels - the Normal channel can be voiced brighter to match the Vibrato channel if you like.
Re: got my pro reverb back from the shop. a few questions:
The first guy doesn't sound like a tech at all.
The second guy sounds like a tech.
Where do you live? Someone here may be close to you and can help you sort things out. Rebiasing an amp is not rocket science. The 5U4 has a lot of sag and will brown your tone, so it will sound different that if it has a GZ34.
The second guy sounds like a tech.
Where do you live? Someone here may be close to you and can help you sort things out. Rebiasing an amp is not rocket science. The 5U4 has a lot of sag and will brown your tone, so it will sound different that if it has a GZ34.
Eardrums!!! We don't need no stinkin' eardrums!
Re: got my pro reverb back from the shop. a few questions:
I don't mean to be offensive here. If you think you might need a bias probe to swap the rectifier tube, you are rather behind the 8 ball on what can and can't be done. It suggests to me that you aren't up to snuff on changing the tone caps. Don't work on this amp yourself. It is dangerous to do so, and you literally have your life at stake if you are unfamiliar with appropriate safety procedures.
As far as the rectifier, the GZ34 and 5U4 are different tubes and can't be swapped without modification. The BF circuit used a GZ34 and you might consider that it is part of the BF sound.
But I'm not convinced that the 45W model can be BF'ed so easily. If you didn't change the output transformer, you missed a key component. One of those (true replica) will set you back $150 or so at Heyboer or Mercury Magnetics. Maybe you can get by without changing the power transformer. I don't know enough about either model amp to offer an opinion on that, but the iron and the speaker both have a lot to do with authentic sound (if there is such a thing).
As far as the rectifier, the GZ34 and 5U4 are different tubes and can't be swapped without modification. The BF circuit used a GZ34 and you might consider that it is part of the BF sound.
But I'm not convinced that the 45W model can be BF'ed so easily. If you didn't change the output transformer, you missed a key component. One of those (true replica) will set you back $150 or so at Heyboer or Mercury Magnetics. Maybe you can get by without changing the power transformer. I don't know enough about either model amp to offer an opinion on that, but the iron and the speaker both have a lot to do with authentic sound (if there is such a thing).
Re: got my pro reverb back from the shop. a few questions:
I'm with dart here. Someone on this board might be happy to help you with it. Give us a location.
The amp will work with a number of rectifiers, including the 5U4G and GZ34.
The amp will work with a number of rectifiers, including the 5U4G and GZ34.
Re: got my pro reverb back from the shop. a few questions:
I assumed that he would have a "tech" do mods by his post, but it is true you can kill yourself right quickly if you don't know what you're doing inside a tube amp.
If there isn't someone here local to you, we may be able recommend someone near you. Or, there are many folks here that take repairs and mods on a mail in basis.
If there isn't someone here local to you, we may be able recommend someone near you. Or, there are many folks here that take repairs and mods on a mail in basis.
Eardrums!!! We don't need no stinkin' eardrums!
Re: got my pro reverb back from the shop. a few questions:
GZ34?
Correct me if I'm wrong, but that amp is designed for the 5U4GB.
And yes, a transformer replacement (both power and output) is
necessary to BF it.
It depends on what kind of tone you're after.
Those SF's are still sweet for clean with a lot of headroom.
If you want sag and distortion, go for whatever it takes to run the GZ34, and take out the mid switch...as well as that output tranny.
Correct me if I'm wrong, but that amp is designed for the 5U4GB.
And yes, a transformer replacement (both power and output) is
necessary to BF it.
It depends on what kind of tone you're after.
Those SF's are still sweet for clean with a lot of headroom.
If you want sag and distortion, go for whatever it takes to run the GZ34, and take out the mid switch...as well as that output tranny.
Re: got my pro reverb back from the shop. a few questions:
Blackfacing isn't always necessarily a good thing.
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: got my pro reverb back from the shop. a few questions:
Sorry for posting and not having anything to add, but something sidehatch wrote attracted my attention:
"2. Rarely there is a weird sound coming thru the amp that sounds like someone it drilling in the other room. Parasitic oscilation? I switched the tubes and it still does it but it only does it maybe once the whole time Im playing thru it . I don't even know how this could be diagnosed or fixed."
I have the same problem in a tube preamp build (M*rshall 2204 circuit), I assumed it was my mixer input, but... no one can help/guide him (and me
) on this point?
sorry for the hijack
Mostro
"2. Rarely there is a weird sound coming thru the amp that sounds like someone it drilling in the other room. Parasitic oscilation? I switched the tubes and it still does it but it only does it maybe once the whole time Im playing thru it . I don't even know how this could be diagnosed or fixed."
I have the same problem in a tube preamp build (M*rshall 2204 circuit), I assumed it was my mixer input, but... no one can help/guide him (and me
) on this point?sorry for the hijack
Mostro
Re: got my pro reverb back from the shop. a few questions:
Thanks for the help everyone.
To answer everyones questions:
No, I didnt change the transformer. I had just about everything changed to get as close to the BF without changing the transformer.
I do know how to discharge the caps to not get shocked/killed but I dont have a lot of tool like a bias probe,scope etc. I have changed pots and caps myself on another amp of mine so I'm certain I can do things like that safely.
I do know a bit about what rectifiers do what as far as sag and have temporarily subbed other rectifiers in but wouldn't take it to a gig like that.
I have been using a carr slant 6 for the past 4 years and Im spoiled because the bias test points are outside the amp and I can swap in a different tube or rectifier and bias myself easlily. I have 2 old fenders now so a bias probe probably wouldn't be a bad idea.
All the techs around here tend to just pop in a tube and call it good. I live in oklahoma city and if anyone is around here I would love to take them up on tweaking the amp a bit.
Te amp does sound really good and I play mostly jazz so the higher headroom of the SF suits me well. I would like to check out the tonestack and see what values are in there and what type of cap they are. I think they are blue mallory's. What is usually prefered in the stack on a BF fender ? Orange drops?
From talking to friend about their amps and what I like it seems that most have a .1, .022 and 250pf silver mica cap in the tonestack. I also would like to know if I have the .001 phase inverter coupling cap. Then I want to find the cause of that oscillation. I need a cool tech to take this thing to!
To answer everyones questions:
No, I didnt change the transformer. I had just about everything changed to get as close to the BF without changing the transformer.
I do know how to discharge the caps to not get shocked/killed but I dont have a lot of tool like a bias probe,scope etc. I have changed pots and caps myself on another amp of mine so I'm certain I can do things like that safely.
I do know a bit about what rectifiers do what as far as sag and have temporarily subbed other rectifiers in but wouldn't take it to a gig like that.
I have been using a carr slant 6 for the past 4 years and Im spoiled because the bias test points are outside the amp and I can swap in a different tube or rectifier and bias myself easlily. I have 2 old fenders now so a bias probe probably wouldn't be a bad idea.
All the techs around here tend to just pop in a tube and call it good. I live in oklahoma city and if anyone is around here I would love to take them up on tweaking the amp a bit.
Te amp does sound really good and I play mostly jazz so the higher headroom of the SF suits me well. I would like to check out the tonestack and see what values are in there and what type of cap they are. I think they are blue mallory's. What is usually prefered in the stack on a BF fender ? Orange drops?
From talking to friend about their amps and what I like it seems that most have a .1, .022 and 250pf silver mica cap in the tonestack. I also would like to know if I have the .001 phase inverter coupling cap. Then I want to find the cause of that oscillation. I need a cool tech to take this thing to!