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Messages - Psabin8951

Tubes and Hybrids / Re: Vox vt120+ combo schematic needed
September 30, 2020, 07:13:32 AM
Yes spot on. They are the same.
Do we think a blown valve would be likely to make C184 "explode"?
Tubes and Hybrids / Vox vt120+ combo schematic needed
September 29, 2020, 12:17:14 PM
Does anyone have a schematic for a vox vt120+ valvetronic combo please.
Or even be able to tell me values for C184 and C185 as both are burnt out erasing markings.
Many thanks
Tubes and Hybrids / Blackstar HT5 noisy Clean channel
August 15, 2020, 09:51:48 AM
I have an early (non reverb) Blackstar HT5 here which has a noisy clean channel which occasionally has volume drop but mainly has a crackle and hiss that appears after about 10 mins of being on.
Both valves have been replaced with new matched ones and all connections have been cleaned, checked and resoldered to eliminate them.
Any thoughts what it could be?
At initial switch on it sounds great.
Ok standby switch was causing an issue.
I'm now getting sound but quiet and distorted on all channels.
I've changed all the tubes and no difference.
Ideas please?
Ok DC voltages with ref to dc gnd are:-
P1 0v
P2 0.1v
P3 0.46v
P4 0.46v
P5 -42v
P6 0v
P7 0v
P8 0v

P1 0v
P2 0.1v
P3 0.39v
P4 0.39v
P5 -42v
P6 0v
P7 0v
P8 0v
Resistantance across tip and sleeve with tubes in is 138k
+15 & -15v supply rails are present
Hi all,
Ok so I got a new transformer from Marshall all fitted ok.
I now get a less bright limiter bulb and no smoking diodes, channel switching works but no sound at all. No sound plugging in to fix return either.
Where do I look next?
With wires from W104 and W105 the limiter bulb still glows brightly and yes standby switch does go to W103 and W106. F102 is ok.
So sounds like I need a new transformer right?
If so can anyone suggest best place to obtain them in the UK?
Sorry, having double checked it glows bright with or without tubes and on standby
Limiter bulb glows even on standby so surely that's not tubes is it?

Limiter already being used and bulb glowing brightly until tubes removed.
Just got back to this.
No fuses blown.
I've replaced the diodes and its definitely not just them.
Does anyone have a pic of what voltages lurk where on the mains transformer as it's not maked. I then can rule that out hopefully.
Thanks in advance
Tubes and Hybrids / JTM60 Combo rectified diodes fried
November 05, 2019, 04:15:27 PM
I have just been given a JTM60 combo.
Its HT rectified diodes D105,106,107,108 are all blown (literally!).
Obviously I can replace these but what would have caused this?
A friend has just got hold of an ENGL Fireball E625 60 watt amp head. Looks in good condition and works but...
When ultra gain switch is turned on there is a large amount of white noise with the guitar sound.
If the guitar is plugged into the effects return and level set to full effect then there is no noise just pure guitar.
Any thoughts on the cause? The seller told him it has had new valves but obviously that's not gospel!
Thanks for the fast reply.
I used a mica sheet plus grease.
Collector shows no connection to heatsink or chassis on meter.
There is continuity back to -V on C61 and DB1