"Mike Gilmour" wrote in message
...
Hiya Keith,

Nice thing about bottle gear, easy to spot the fault and get to. Seeing
R6
cooked (screen grid resistor?) why did it get mucho grid current I'm
thinking? It may be worth keeping an eye on it even if you've swapped out
the tube. But I think possibly that coupling cap was leaky giving +ve to
G1
driving plate current hard and screen grid current burning R6 - Good job
Keith you've got the problem all sorted for Crimbo :-)
Cheers,

Mike



Hi Mike,

Well, fingers crossed, it's been running for 6 hours straight now and no
sign of overheating. (Room's like an oven, of course!)

I'm blaming the Czech KT88s arcing over for the two instances I've had of a
brew-up with this amp in the last two years, but I'm always eager to learn,
if you think there might another likely cause of this problem I would be
very interested to hear it. Personally, I think it's a sussy little bugger
(Kit88) anyway because WAD didn't keep it on the books for long - superb
sound quality but possibly not too stable? (I really ought to get on to the
WAD forum and see what the 'word on the street' is!)

Don't know what anyone else here might think of a KT88/6550C comparison but
it seems the bass is even more thunderous than it was??? (It ain't got the
biggest OPTs in the world but it's never been too 'polite'.....!!)

(Btw, we're on holiday now so might finally get round to that Black Isle
proggie we've got recorded! :-)

Hi Keith,

Reckon you already nailed the problem caused I guess by that failed coupling
cap. Did the cooked resistors burn the pcb at all? - sometimes standing them
off a bit avoids that damage should it happen again. I've also had the
very occasional '88 flashover on Svets that seems to be just down to a rogue
tube, swapping it out has cured it.
KT88 vs 6550, my experience is the '88 are much more musical but ultimately
don't have the same clout. The bass from the 6550 seems more powerful but
not necessarily as sweet..but this varies a hell of a lot from amp to amp so
I guess its just horses for courses in the end - whatever suits your
particular system. I sometimes change from KT90's to 6550's to KT88's just
to enjoy the strengths of each - none is perfect but an orchestral symphony
sounds just great with '88's and Black Sabbath with 90's with the 6550's
serving most other listening.
I've hit your site a couple of times - hows the hit counter doing??

Mike

"Keith G" wrote in message
...

"Mike Gilmour" wrote in message
...
Hiya Keith,

Nice thing about bottle gear, easy to spot the fault and get to. Seeing
R6
cooked (screen grid resistor?) why did it get mucho grid current I'm
thinking? It may be worth keeping an eye on it even if you've swapped
out
the tube. But I think possibly that coupling cap was leaky giving +ve to
G1
driving plate current hard and screen grid current burning R6 - Good
job
Keith you've got the problem all sorted for Crimbo :-)
Cheers,

Mike



Hi Mike,

Well, fingers crossed, it's been running for 6 hours straight now and no
sign of overheating. (Room's like an oven, of course!)

I'm blaming the Czech KT88s arcing over for the two instances I've had of
a
brew-up with this amp in the last two years, but I'm always eager to
learn,
if you think there might another likely cause of this problem I would be
very interested to hear it. Personally, I think it's a sussy little bugger
(Kit88) anyway because WAD didn't keep it on the books for long - superb
sound quality but possibly not too stable? (I really ought to get on to
the
WAD forum and see what the 'word on the street' is!)

Don't know what anyone else here might think of a KT88/6550C comparison
but
it seems the bass is even more thunderous than it was??? (It ain't got the
biggest OPTs in the world but it's never been too 'polite'.....!!)

(Btw, we're on holiday now so might finally get round to that Black Isle
proggie we've got recorded! :-)

"Mike Gilmour" wrote in message
...
Hi Keith,

Reckon you already nailed the problem caused I guess by that failed
coupling
cap. Did the cooked resistors burn the pcb at all?


Just a tad! - See

http://www.apah69.dsl.pipex.com/keith_g/show/burn1.JPG

and

http://www.apah69.dsl.pipex.com/keith_g/show/burn2.JPG

- sometimes standing them
off a bit avoids that damage should it happen again.


Yes, I think I should have stood them off a bit more than I did (others are
stood off by a good cm or so), but it don't help that the 'component side'
of the board is actually the underside in use! (If the tracks do get burned
off in the future, it won't be the first board I've had to augment with a
bit of 'hard wiring' !! :-)


I've also had the
very occasional '88 flashover on Svets that seems to be just down to a
rogue
tube, swapping it out has cured it.


I think I've had 3 or 4 go in the last 2 years with this amp.....


KT88 vs 6550, my experience is the '88 are much more musical but
ultimately
don't have the same clout. The bass from the 6550 seems more powerful but
not necessarily as sweet..


That's exactly what I'm getting! - No less pleasing overall but a bit
'different' to what I've been used to.


but this varies a hell of a lot from amp to amp so
I guess its just horses for courses in the end - whatever suits your
particular system. I sometimes change from KT90's to 6550's to KT88's just
to enjoy the strengths of each - none is perfect but an orchestral
symphony
sounds just great with '88's and Black Sabbath with 90's with the 6550's
serving most other listening.
I've hit your site a couple of times - hows the hit counter doing??


Heh heh! I just checked and was visitor No. 10,000!!! Thanks for your help,
Mike!

:-)

Have you tried the Russian Teflon coupling caps? Cheap and very good - just a
bit big. I just love them. Neutral and very detailed. Talking big, I use motor
run polyprop caps (40uF) in the PSU with a choke CLC. Depends on the real
estate of the amp - not expensive and I'm surprised no commercial amps use
them. Much faster and more detailed. Andy

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

"Andy Evans" wrote in message
...
Have you tried the Russian Teflon coupling caps? Cheap and very good -
just a
bit big. I just love them. Neutral and very detailed. Talking big, I use
motor
run polyprop caps (40uF) in the PSU with a choke CLC. Depends on the real
estate of the amp - not expensive and I'm surprised no commercial amps use
them. Much faster and more detailed. Andy



Andy, I've resisted Nick G's exhortations to mess with the KiT88 for a while
now! But, apart from a general cluelessness on my part, there really isn't
much room inside it and the use of a PCB don't help matters much. I have
another amp which desperately needs a service ('cattle trucked' atm!) and
I'm thinking to butcher it into summat different-looking in the new year and
hoping to learn a bit on the way......

"Andy Evans" wrote in message
...
Have you tried the Russian Teflon coupling caps? Cheap and very good -
just a
bit big. I just love them. Neutral and very detailed. Talking big, I use
motor
run polyprop caps (40uF) in the PSU with a choke CLC. Depends on the real
estate of the amp - not expensive and I'm surprised no commercial amps use
them. Much faster and more detailed. Andy



Andy, I've resisted Nick G's exhortations to mess with the KiT88 for a while
now! But, apart from a general cluelessness on my part, there really isn't
much room inside it and the use of a PCB don't help matters much. I have
another amp which desperately needs a service ('cattle trucked' atm!) and
I'm thinking to butcher it into summat different-looking in the new year and
hoping to learn a bit on the way......

Have you tried the Russian Teflon coupling caps? Cheap and very good - just a
bit big. I just love them. Neutral and very detailed. Talking big, I use motor
run polyprop caps (40uF) in the PSU with a choke CLC. Depends on the real
estate of the amp - not expensive and I'm surprised no commercial amps use
them. Much faster and more detailed. Andy

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

"Mike Gilmour" wrote in message
...
Hi Keith,

Reckon you already nailed the problem caused I guess by that failed
coupling
cap. Did the cooked resistors burn the pcb at all?


Just a tad! - See

http://www.apah69.dsl.pipex.com/keith_g/show/burn1.JPG

and

http://www.apah69.dsl.pipex.com/keith_g/show/burn2.JPG

- sometimes standing them
off a bit avoids that damage should it happen again.


Yes, I think I should have stood them off a bit more than I did (others are
stood off by a good cm or so), but it don't help that the 'component side'
of the board is actually the underside in use! (If the tracks do get burned
off in the future, it won't be the first board I've had to augment with a
bit of 'hard wiring' !! :-)


I've also had the
very occasional '88 flashover on Svets that seems to be just down to a
rogue
tube, swapping it out has cured it.


I think I've had 3 or 4 go in the last 2 years with this amp.....


KT88 vs 6550, my experience is the '88 are much more musical but
ultimately
don't have the same clout. The bass from the 6550 seems more powerful but
not necessarily as sweet..


That's exactly what I'm getting! - No less pleasing overall but a bit
'different' to what I've been used to.


but this varies a hell of a lot from amp to amp so
I guess its just horses for courses in the end - whatever suits your
particular system. I sometimes change from KT90's to 6550's to KT88's just
to enjoy the strengths of each - none is perfect but an orchestral
symphony
sounds just great with '88's and Black Sabbath with 90's with the 6550's
serving most other listening.
I've hit your site a couple of times - hows the hit counter doing??


Heh heh! I just checked and was visitor No. 10,000!!! Thanks for your help,
Mike!

:-)

Hi Keith,

Reckon you already nailed the problem caused I guess by that failed coupling
cap. Did the cooked resistors burn the pcb at all? - sometimes standing them
off a bit avoids that damage should it happen again. I've also had the
very occasional '88 flashover on Svets that seems to be just down to a rogue
tube, swapping it out has cured it.
KT88 vs 6550, my experience is the '88 are much more musical but ultimately
don't have the same clout. The bass from the 6550 seems more powerful but
not necessarily as sweet..but this varies a hell of a lot from amp to amp so
I guess its just horses for courses in the end - whatever suits your
particular system. I sometimes change from KT90's to 6550's to KT88's just
to enjoy the strengths of each - none is perfect but an orchestral symphony
sounds just great with '88's and Black Sabbath with 90's with the 6550's
serving most other listening.
I've hit your site a couple of times - hows the hit counter doing??

Mike

"Keith G" wrote in message
...

"Mike Gilmour" wrote in message
...
Hiya Keith,

Nice thing about bottle gear, easy to spot the fault and get to. Seeing
R6
cooked (screen grid resistor?) why did it get mucho grid current I'm
thinking? It may be worth keeping an eye on it even if you've swapped
out
the tube. But I think possibly that coupling cap was leaky giving +ve to
G1
driving plate current hard and screen grid current burning R6 - Good
job
Keith you've got the problem all sorted for Crimbo :-)
Cheers,

Mike



Hi Mike,

Well, fingers crossed, it's been running for 6 hours straight now and no
sign of overheating. (Room's like an oven, of course!)

I'm blaming the Czech KT88s arcing over for the two instances I've had of
a
brew-up with this amp in the last two years, but I'm always eager to
learn,
if you think there might another likely cause of this problem I would be
very interested to hear it. Personally, I think it's a sussy little bugger
(Kit88) anyway because WAD didn't keep it on the books for long - superb
sound quality but possibly not too stable? (I really ought to get on to
the
WAD forum and see what the 'word on the street' is!)

Don't know what anyone else here might think of a KT88/6550C comparison
but
it seems the bass is even more thunderous than it was??? (It ain't got the
biggest OPTs in the world but it's never been too 'polite'.....!!)

(Btw, we're on holiday now so might finally get round to that Black Isle
proggie we've got recorded! :-)

Keith G wrote:



Don't know what anyone else here might think of a KT88/6550C comparison but
it seems the bass is even more thunderous than it was??? (It ain't got the
biggest OPTs in the world but it's never been too 'polite'.....!!)

Have a look at this, it may help

http://www.worldaudiodesign.co.uk/fo...ght=6550+kat88

--
Nick