Buzz, Thunk. Uh oh.

Rox

So, just turned my Vox AD60VT on, a short buzz, and then nothing. Power light goes off.  Dead.

I've made sure the power cable is fine with my multimeter in case the fuse had gone - it hasn't.

So er... what do I do now?

I've got all the delicate equipment required for a fix job with guidance - a screwdriver and a lump hammer. 

ICBM

Take it to a tech.

It will have blown the internal fuse. The cause of this is almost certainly a blown power transistor or rectifier diode, which are the only faults I've ever seen with these. (Other than a poor connection in the Ext speaker jack, which doesn't blow the fuse.)

The bad news is that they're a bit of a faff to work on. The good news is that unlike a lot of modern amps they use sensible large-scale, discrete components (al least in the analogue/power sections) which are both obtainable and easy to replace.

Rox

Thanks muchly @ICBM - there aren't many options in my locale for amp techs, but I'll start my search.

Bit of a deadspot up here (North Lincs between Scunthorpe and Gainsborough), I can't find a local guitar tech either. 

lewism

HiQ got recommended in the sticky at the top of the Amps section. They're behind the Lincolnshire Showground on Burton Road (B1398) as you come into Lincoln from the North. I've not used them but been meaning to try them.  I don't think amp repairs are their main business but it's listed on their website. Alternatively, I've used Valve Amp Hospital in Nottingham and been very happy but not sure if he's taking on work at the moment.

Rox

I've just found a chap a couple of miles away that does amp repairs and I've emailed him, so hopefully I won't have a longer journey to go on!

I might ask him if he knows anyone that does setups locally too as it all seems a little empty for guitar services up here.

hywelg

Plenty of options.in Nottingham, Dave Hunter @DJH83004,  and Dave Ball (search recommended amp techs for contact details).

DJH83004

If you are struggling to find someone locally, I'll be happy to have a look at for you, based in North Notts, so for you it would be head for Newark, then through Southwell, to where I am based.  

Rox

Thanks @hywelg and @DJH83004 - I really appreciate it, especially as you seem really busy @DJH83004 ;   The local chap has gotten back to me, and should be able to take a look at it next week, so fingers crossed.

I must admit, after moving house, this amp was languishing in the cupboard.  It was only when I wanted some more sounds to play with I brought it back out - I'd not played through it in a year.

No kidding, the sounds are brilliant.  I also have the metal grilled AD30VT (I have it in my workshop just to test if things are working) which I brought over to the house when this one died.  In comparison, it isn't anywhere near as good.  Less options, sound not so good...

I just hope the problem isn't terminal - because it looks like buying one of these ain't cheap anymore, but I will keep the thread updated. 

Rox

Just dropped it off, so fingers crossed!

Rox

The repair chap says that the Valve is not working correctly, but all the output devices and semiconductors are working. However, the amp keeps blowing fuses in mains IEC socket.  He says he's tested the transformer and also seems to work ok... so he's still looking for the problem.

DJH83004

Well one should never criticise unfinished work, but if the mains tx is testing ok, and the correct level of DC is present then the output stage is the next likely culprit, not sure what ' the valve not working correctly' actually means, the VT amps are quite unconventional mind, and not the easiest to work on.

ChuckManual

Not to detract from your woes (and I hope your Vox is fixed soon), but; "Buzz", "Thunk" and "Uh-Oh!" sound like great controls for an amp!

They should be on a distortion pedal, at least!

Where's @ThorpyFX when you need him...?

ICBM

Rox said:

The repair chap says that the Valve is not working correctly, but all the output devices and semiconductors are working. However, the amp keeps blowing fuses in mains IEC socket.  He says he's tested the transformer and also seems to work ok... so he's still looking for the problem.

If it's blowing mains fuses it can really only be -

Power transformer
Rectifier diode
Voltage regulator
Power transistor
Or just possibly a shorted speaker (this is very rare).

If it's blowing the mains fuse it can't be the rectifiers for the 8V LT supply or the HT for the valve, since they're separately fused internally, as is the filament supply to the valve. If it's not the transformer it must be in the main power circuit.

It's odd that he thinks the valve isn't working properly since it would be unusual to have two unrelated faults simultaneously, but neither possible valve fault could blow the mains fuse.

ThorpyFX

ChuckManual said:

Not to detract from your woes (and I hope your Vox is fixed soon), but; "Buzz", "Thunk" and "Uh-Oh!" sound like great controls for an amp!

They should be on a distortion pedal, at least!

Where's @ThorpyFX when you need him...?

Hahah those controls would anger loads of people...... ore reason to do it. 

Rox

You need one with "Wham" "Bam" and "Thank You Ma'am"

Rox

Thanks for your input, @DJH83004 and @ICBM - he says he'll mail me again on Monday, so we'll see what happens. 

Rox

He's said he needs to replace the Bridge Rectifier..?

ICBM

Rox said:

He's said he needs to replace the Bridge Rectifier..?

That sounds a likely candidate.

Rox

Well, the amp is back home and working again.  Sounds brilliant.. so relieved it wasn't terminal...