Greetings everybody!
Firstly, apologies if I've upset anyone thinking that I'm needlessly butchering one of Ampeg's classic vintage amps...
This particular example has willingly donated it's body for research - in fact one or two of you may have seen this one before. After I got it I saw a thread where somebody was asking if they thought a B25 in a shop was worth buying and one of the replies had words along lines of, "Is that the one in (whichever shop it was) with its guts hanging out the back of it with some bits missing?"
It was, and the OP hadn't bought it, but I had - and not only that, I had it carted all the way to the UK.....!!! Mind you I got it for a song and there were over two dollars to the pound at the time which helped.
When it arrived it was looking a little sorry for itself. One of the 6L6GC valves had a cracked base and it was generally rather tatty. I replaced both of the output valves, cobbled together an adjustable bias pot and very nervously fired it up. I set the bias as closely as I could but the B+ was all over the place, almost certainly down to what appeared to be the original caps in it.
I powered it down, drained the caps and that was it for a few years as life took over.
A couple of weeks ago, after finishing another project I decided to have another look at this fella and get some experience with valve/tube amps by turning it into a learning project. I had a few ideas and preferences I wanted to try and felt I could implement them on this and gain some experience at the same time. I've relatively little knowledge of electronic theory but maybe I can pick something up on the way and hopefully somebody else will gain something too.
As it was -
![[Image: IMG_20150328_082734_zpsib6szdl8.jpg]](http://i848.photobucket.com/albums/ab42/2KARABASH/IMG_20150328_082734_zpsib6szdl8.jpg)
I replaced the two 30uf 600v dynamite stick caps with four F+T 32uf+32uf 500v caps on a piece of circuit board mounted on the output transformer bolts.
![[Image: IMG_20150410_0715102_zpslefnwcxs.jpg]](http://i848.photobucket.com/albums/ab42/2KARABASH/IMG_20150410_0715102_zpslefnwcxs.jpg)
Underneath the new board.
![[Image: IMG_20150410_0634502_zps0do4tkv2.jpg]](http://i848.photobucket.com/albums/ab42/2KARABASH/IMG_20150410_0634502_zps0do4tkv2.jpg)
The 40uf+40uf cap was replaced by an F+T 50uf+50uf 500v in the same position as the original with a plastic clamp.
That's it for the moment. I've already had some much appreciated help from BassHog on another forum. Any constructive criticism is most welcome and thanks for putting up with my waffling post.
All the best
Grahame
Firstly, apologies if I've upset anyone thinking that I'm needlessly butchering one of Ampeg's classic vintage amps...
This particular example has willingly donated it's body for research - in fact one or two of you may have seen this one before. After I got it I saw a thread where somebody was asking if they thought a B25 in a shop was worth buying and one of the replies had words along lines of, "Is that the one in (whichever shop it was) with its guts hanging out the back of it with some bits missing?"
It was, and the OP hadn't bought it, but I had - and not only that, I had it carted all the way to the UK.....!!! Mind you I got it for a song and there were over two dollars to the pound at the time which helped.
When it arrived it was looking a little sorry for itself. One of the 6L6GC valves had a cracked base and it was generally rather tatty. I replaced both of the output valves, cobbled together an adjustable bias pot and very nervously fired it up. I set the bias as closely as I could but the B+ was all over the place, almost certainly down to what appeared to be the original caps in it.
I powered it down, drained the caps and that was it for a few years as life took over.
A couple of weeks ago, after finishing another project I decided to have another look at this fella and get some experience with valve/tube amps by turning it into a learning project. I had a few ideas and preferences I wanted to try and felt I could implement them on this and gain some experience at the same time. I've relatively little knowledge of electronic theory but maybe I can pick something up on the way and hopefully somebody else will gain something too.
As it was -
I replaced the two 30uf 600v dynamite stick caps with four F+T 32uf+32uf 500v caps on a piece of circuit board mounted on the output transformer bolts.
Underneath the new board.
The 40uf+40uf cap was replaced by an F+T 50uf+50uf 500v in the same position as the original with a plastic clamp.
That's it for the moment. I've already had some much appreciated help from BassHog on another forum. Any constructive criticism is most welcome and thanks for putting up with my waffling post.
All the best
Grahame