I bought a Chinese valve amp (Yaoin 300B job), on Ebay. Like this one:

http://cgi.ebay.co.uk/300B-High-End-...QQcmdZViewItem

It worked great for quite a while and I enjoyed the sound.
Now the left channel has gone dodgy. The music is still barely "there", but
all scratchy and weak. The right channel is fine.
I've swapped leads and connectors to establish that the speakers/cables/CD
player are not at fault. It definitely seems to be the amplifier. The left
output valve doesn't get as hot as the right one. Swapping the valves
indicates that the valve is not the problem.

Can anyone suggest a solution (other than using it as the world's heaviest
paperweight)?

I live in the North West of England. Is there anyone in the region who could
fix it?

Thanks for any help.

Steve

Same here dude.

I'm in Manchester, BTW. I bought a YaQin (not Yaoin, BTW) amp back
in summer 2004. Worked a charm and sounded beautiful for a few weeks,
and then BANG! Resistors started burning out, and that caused valves to
have internal firework shows, which caused further overcurrent.

Mine too has always been more of a PITA on the left channel, though
that'll only be coincidence.

Right now, the right-hand channel is fine. The left is ****ed; it just
sounds far too quiet, "scratchy" as you put it, and "early-clippy".

When it works/worked properly, it was like a beautiful, but
high-maintenance girlfriend: Fantastic and "Ooooooh!" but a moody
pain in the ****ing arse a lot of the time, that demands too much attention
when it really should be just cutting the crap and be getting on with letting
us both have a good time. That's the best analogy I can give.

Bummer, but I don't have a 'scope, so I've no real chance of fixing
it, I don't think.

I feel your pain!


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.livejournal.com/userinfo.bml?user=fleetie

"Steve" wrote in message
...
I bought a Chinese valve amp (Yaoin 300B job), on Ebay. Like this one:

http://cgi.ebay.co.uk/300B-High-End-...QQcmdZViewItem

It worked great for quite a while and I enjoyed the sound.
Now the left channel has gone dodgy. The music is still barely "there",
but all scratchy and weak. The right channel is fine.
I've swapped leads and connectors to establish that the speakers/cables/CD
player are not at fault. It definitely seems to be the amplifier. The left
output valve doesn't get as hot as the right one. Swapping the valves
indicates that the valve is not the problem.

Can anyone suggest a solution (other than using it as the world's heaviest
paperweight)?

I live in the North West of England. Is there anyone in the region who
could fix it?

Thanks for any help.


I have fixed quite a few of 'em in the past year. They usually have
simple but sometimes terminal (i.e fatal) faults. They range from
simple dry solder joints, or failed coupling caps, or intermittent
bias pots, to open circuit windings on the OPT.

The are people on RAT (rec.audio.tubes) who will probably been able
to pinpoint the fault from your description and further
discussion. Patrick Turner is especially knowledgeable, but holds
most Chinese products in low esteem. Many of them use poor quality
components and woefully poor/small transformers, which are hidden
inside large impressive-looking pots, sometimes filled with cat litter as a
potting compound.

At least you have one working channel, one which you can take DC
voltage measurements and compare with the broken channel. That's
the fastest way to fault find. But take great care. Even with the amp
switched off and unplugged there can still be high voltages on the
power supply capacitors.

Recently, while in Vietnam - I cam across a tube amp shop in Saigon.
I told the salesman I was interested in buying in quantity, and he offered
me "any ten amplifiers for USD1000" I have a feeling there would
also have been considerable room for negotiation in that price!!

One cannot even buy a proper UK built 300B output transformer
for the price of a complete Chinky amplifier.. Caveat emptor:-)

It's good that people are interested in thermionic audio, but sadly
they may get the wrong impression regarding reliability from a
Chinese-built product.

Tube amps can and should be reliable. I have a friend in Sweden
who is a bespoke amp builder. He offers a ten year warranty on
his work. He has been in business some twenty years, and has never
had amp returned for more than routine service.

Good luck

Iain

My take on Chinese amps is that they are basically kits of parts,
nominally put together in working condition. They're worth it for the
parts - if they are cheap enough after importing. This suits a
competent builder, who can immediately start replacing parts and who
can fault find reasonably well. Something like the equivalent of an un-
reconditioned old Leak amp with leaky caps and out of spec resistors.

But add on the import duty and this comes to over ?700. This buys a
better valve amp on the second-hand market. Like a re-conditioned Leak
for instance. Better? Well, I'd prefer a 300b. But a Leak will hold
its value, is substantially built and can be tweaked to sound really
nice. But there are quite a variety of valve amps about these days,
and I wouldn't be surprised if ?700 would get you a nice Yank amp or a
boutique UK one.

"Iain Churches" wrote


snip wise words - except the bit about the Sinophobic RATs


One cannot even buy a proper UK built 300B output transformer
for the price of a complete Chinky amplifier.. Caveat emptor:-)

It's good that people are interested in thermionic audio, but sadly
they may get the wrong impression regarding reliability from a
Chinese-built product.

Tube amps can and should be reliable. I have a friend in Sweden
who is a bespoke amp builder. He offers a ten year warranty on
his work. He has been in business some twenty years, and has never
had amp returned for more than routine service.


It's the old ''the Chinky Cheepy you can afford sounds better than the
*audio bling* you can't afford (or don't want to spend the money on)"
argument again, isn't it?

(How long it may *sound* is another matter and the luck of the draw, of
course...! ;-)

Steve wrote:
I bought a Chinese valve amp (Yaoin 300B job), on Ebay. Like this one:

http://cgi.ebay.co.uk/300B-High-End-...QQcmdZViewItem

It worked great for quite a while and I enjoyed the sound.
Now the left channel has gone dodgy. The music is still barely
"there", but all scratchy and weak. The right channel is fine.
I've swapped leads and connectors to establish that the
speakers/cables/CD player are not at fault. It definitely seems to be
the amplifier. The left output valve doesn't get as hot as the right
one. Swapping the valves indicates that the valve is not the problem.

Can anyone suggest a solution (other than using it as the world's
heaviest paperweight)?

I live in the North West of England. Is there anyone in the region
who could fix it?

Thanks for any help.

Steve

I'm in Stockport and restore valve radios as a hobby.
I'd be happy to look at it, and repair it if it's a fairly common component
at fault.
Martin.

Martin Crossley wrote:


I'm in Stockport and restore valve radios as a hobby.
I'd be happy to look at it, and repair it if it's a fairly common component
at fault.
Martin.




I would guess Stockport is nearer to you, but I am in the general area
of Halifax, if you need any more help.

--
Nick

"Steve" wrote in message
...
I bought a Chinese valve amp (Yaoin 300B job), on Ebay. Like this one:

http://cgi.ebay.co.uk/300B-High-End-...QQcmdZViewItem



Why do you say 'That'll teach me'??

Like you could have bought a Border Patrol 300B amp (say) for anything
upwards of 4K:

http://www.users.globalnet.co.uk/~va...rPatrolAmp.htm

http://www.borderpatrol.co.uk/amprev.htm


....but chose the Chinaman for what - less than 400 quid instead? (You
get what you pay for in this life!! :-)

Anyway, I see you've had a couple of kind offers of help already -
expect to pay for some parts, needless to say...

"Keith G" wrote in message
...


Why do you say 'That'll teach me'??

Disappointment at the failure, and sick realization that I couldn't really
send it back.
Darned thing sat there looking accusingly at me for months every time I went
into the "office".

Now the offers of help from a couple of the board members has improved my
outlook.


Like you could have bought a Border Patrol 300B amp (say) for anything
upwards of 4K:

http://www.users.globalnet.co.uk/~va...rPatrolAmp.htm

http://www.borderpatrol.co.uk/amprev.htm



No, but I could have bought a used Sugden Class A amp, for example?


...but chose the Chinaman for what - less than 400 quid instead? (You get
what you pay for in this life!! :-)

Anyway, I see you've had a couple of kind offers of help already - expect
to pay for some parts, needless to say...


Yes!

Steve wrote:

I bought a Chinese valve amp (Yaoin 300B job), on Ebay. Like this one:


http://cgi.ebay.co.uk/300B-High-End-...QQcmdZViewItem

It worked great for quite a while and I enjoyed the sound.
Now the left channel has gone dodgy. The music is still barely "there",
but all scratchy and weak. The right channel is fine.
I've swapped leads and connectors to establish that the speakers/cables/CD
player are not at fault. It definitely seems to be the amplifier. The left
output valve doesn't get as hot as the right one. Swapping the valves
indicates that the valve is not the problem.

Can anyone suggest a solution (other than using it as the world's heaviest
paperweight)?

I live in the North West of England. Is there anyone in the region who
could fix it?

Thanks for any help.

Steve

If all else fails, you can use the good channel for karaoke, you won't need
a mic, just sing into the 12AT7 on the front end.

If you get it fixed, do replace the 12AT7s with 12AU7s or 12AX7s

Keith