VH4 Problem

[DiezelDale]

Peter,
My VH4 is having some significant issue, when I power the amp on I get a low volume buzz for sound? my power tubes are good and I checked and trouble shot all the pre-amp tubes? Is there a Diezel repair tech near Colorado, USA?

 

[MARK2C]

Check any internal fuses first. Most VH4's had internal fuses for the heaters, B+ preamp rail and PI B+.

If the amp starts up and channel switches but has no sound you could have a blown hum trimmer
or the rectifier bridge for the preamp heaters went bad. The preamp tubes would not light up.

The Hum Trimmer should read 50 Ohm with the arrow at 6:00 facing the front of the chassis.

If the amp turns on but does not cycle the relays or channel switch, look at the fuses on the midi board.

If all the fuses and the hum trimmer check out, look at the filter caps for bulges or leakage of yellow goo.

 

[Mr. Q]

What is this element marked with red arrow, may I ask?



I was trying to bias my VH4 today and something strange has happened - after turning the standby to run position one tube overheated very quickly and blew out the tube fuse and main power fuse as well. The red diode is broken and the thing marked on the picture has cracked apart (the white ceramic cover).

After while I changed the main fuse and turned the amp on for a few seconds (on the stanby of course), but I don't know what to do next? What has really happened? And is there possibility that other parts of the amp has been damaged too? Can anyone help?

 

[DiezelDale]

Thanks for the trouble shooting tips! I pulled the chasis out and noticed one of my Filter Caps is growing a second head, well more like it was clubbed by polizei after a bad night drinking! Those guy's have some serious spring loaded batans! I know from experience. Anyone know what may cause this or was it just time for that cap?

Peter D.
, are parts like this under the owner warranty or is it like tubes, normal wear items?

 

[MARK2C]

What is this element marked with red arrow, may I ask?



I was trying to bias my VH4 today and something strange has happened - after turning the standby to run position one tube overheated very quickly and blew out the tube fuse and main power fuse as well. The red diode is broken and the thing marked on the picture has cracked apart (the white ceramic cover).

After while I changed the main fuse and turned the amp on for a few seconds (on the stanby of course), but I don't know what to do next? What has really happened? And is there possibility that other parts of the amp has been damaged too? Can anyone help?

That resistor, if I recall holds the LED above ground reference or drops the forward voltage. When the fuse blows do to a surge to ground it bypasses the resistor
and the LED turns on. If you have a MASSIVE surge to ground from loose socket pins or catastrophic power tube failure or a long enough
period of red plating the resistor will blow. Basically, you had a bad tube or your tube pins on that socket are seriously stretched and shorted the tube to ground.
The wire element in the resistor got so hot it exploded the ceramic. Nothing else is harmed and you just need to replace the 4.7K 5 Watt resistor and LED and you
will be fine. Note the Anode of the LED and snip the correct lead like Diezel does so you don't put it in backwards. Also double check for any carbon build up in the fuse socket from the tube fault fuse blowing and clean it off.

 

[MARK2C]

Thanks for the trouble shooting tips! I pulled the chasis out and noticed one of my Filter Caps is growing a second head, well more like it was clubbed by polizei after a bad night drinking! Those guy's have some serious spring loaded batans! I know from experience. Anyone know what may cause this or was it just time for that cap?

Peter D.
, are parts like this under the owner warranty or is it like tubes, normal wear items?

Good work !!!!

Caps are only as good as you can buy them and they don't make them like the Daly's or LCR's these days. They are really easy to change in the VH4.
You should be able to get F&T's for $ 10.00 each, just make sure the clamps are the same size. With most companies, after one year it's a wear item.
They should generally be replaced between 8 and 10 years of use.

Good Luck.

 

[Ventura]

MARK2C.... You are DAMN good!!!! Serious " "!!!!

Golden man, just golden!!

V.

 

[Peter Diezel]

The filter caps can get bulbs from the heat, but
I´m not sure that they are broken.

Please check it out and send an email to
peterdiezel (at) diezelamplification (dot) com

 

[Mr. Q]

What is this element marked with red arrow, may I ask?



I was trying to bias my VH4 today and something strange has happened - after turning the standby to run position one tube overheated very quickly and blew out the tube fuse and main power fuse as well. The red diode is broken and the thing marked on the picture has cracked apart (the white ceramic cover).

After while I changed the main fuse and turned the amp on for a few seconds (on the stanby of course), but I don't know what to do next? What has really happened? And is there possibility that other parts of the amp has been damaged too? Can anyone help?

That resistor, if I recall holds the LED above ground reference or drops the forward voltage. When the fuse blows do to a surge to ground it bypasses the resistor
and the LED turns on. If you have a MASSIVE surge to ground from loose socket pins or catastrophic power tube failure or a long enough
period of red plating the resistor will blow. Basically, you had a bad tube or your tube pins on that socket are seriously stretched and shorted the tube to ground.
The wire element in the resistor got so hot it exploded the ceramic. Nothing else is harmed and you just need to replace the 4.7K 5 Watt resistor and LED and you
will be fine. Note the Anode of the LED and snip the correct lead like Diezel does so you don't put it in backwards. Also double check for any carbon build up in the fuse socket from the tube fault fuse blowing and clean it off.

You're the man, seriously - many thanks for that info - you made my day! Quick reply and detailed info - really appreciate it. It looks like an easy job for the tech.
That's probably the reason of it all - broken tube base:

Thank God it didn't happen at the gig.

Any chances that you know tech. spec. of that diode?

 

[MARK2C]

What is this element marked with red arrow, may I ask?



I was trying to bias my VH4 today and something strange has happened - after turning the standby to run position one tube overheated very quickly and blew out the tube fuse and main power fuse as well. The red diode is broken and the thing marked on the picture has cracked apart (the white ceramic cover).

After while I changed the main fuse and turned the amp on for a few seconds (on the stanby of course), but I don't know what to do next? What has really happened? And is there possibility that other parts of the amp has been damaged too? Can anyone help?

That resistor, if I recall holds the LED above ground reference or drops the forward voltage. When the fuse blows do to a surge to ground it bypasses the resistor
and the LED turns on. If you have a MASSIVE surge to ground from loose socket pins or catastrophic power tube failure or a long enough
period of red plating the resistor will blow. Basically, you had a bad tube or your tube pins on that socket are seriously stretched and shorted the tube to ground.
The wire element in the resistor got so hot it exploded the ceramic. Nothing else is harmed and you just need to replace the 4.7K 5 Watt resistor and LED and you
will be fine. Note the Anode of the LED and snip the correct lead like Diezel does so you don't put it in backwards. Also double check for any carbon build up in the fuse socket from the tube fault fuse blowing and clean it off.

You're the man, seriously - many thanks for that info - you made my day! Quick reply and detailed info - really appreciate it. It looks like an easy job for the tech.
That's probably the reason of it all - broken tube base:

Thank God it didn't happen at the gig.

Any chances that you know tech. spec. of that diode?

Since your in the EU I would buy the resistor and LED from Diezel to get the proper match.

Don't forget to tighten those power tube socket pins...

 

[Mr. Q]

Since your in the EU I would buy the resistor and LED from Diezel to get the proper match.

Don't forget to tighten those power tube socket pins...

That's a great idea! I'll contact Peter tommorow. Once again - many thanks for help.

 

[Mailman1971]

These threads are PRICELESS!!
So much info!!

 

[MOOSEHEADS]

These threads are PRICELESS!!
So much info!!

The pics are the best I really like the arrows pointing to the part.

 

[Ventura]

These threads are PRICELESS!!
So much info!!

The pics are the best I really like the arrows pointing to the part.

Jaaayazeeeus Mooseheads, WTF is happening to your avatar man?!?!?!?! Frightening. Must be a Canadian thing or something...

V.

 

[MARK2C]

In all the years (11) of Diezel ownership, 98% of any issues were tube, fuse or rarely cap related.
As I mentioned in another post, I almost had a Blue Face !!! I settled for a black face but it didn't
even have a bias pot back then. Damn, I'm getting old !!!!

I'm just trying to give papa a break so he can finish Hagen.......

 

[Peter Diezel]

Thank You, Darling

 

[MARK2C]

Thank You, Darling

Your welcome Papa !!!

Now finish that Marlboro Menthol and get back to work !!!!!!!