Laney sound fades out, then comes back

[Emetal]

Laney VH100R problem: when worms up, sound suddenly fades out, then after few seconds or minutes comes back. Keeps repeating. It kind of feels like somebody turns off the Stand By Switch then turns it on again. All preamp and power tubes changed, biased at about 70%. Tubes, cables and guitar problems ruled out. It effects all channels, and both preamp and power amp section, as I sad like somebody turns off and on Stand by switch. Heaters and pilot lites keeps working, sound goes away.. I am looking at page 4 of Schematic, at that Relay 5 and or TS9 could it be any of those?? Any other ideas??

[The Dude]

Before you go replacing those parts, monitor your B+ see if it drops out when you have the symptoms. Relay 5 and TS9 are part of a delay turn on circuit that switches B+ to the amp. So, see if you still have B+ after the relay when the amp cuts out.

[g1]

both preamp and power amp section, as I sad like somebody turns off and on Stand by switch.

So the problem happens when you put signal in at the 'Power Amp In' jack?

[Emetal]

So the problem happens when you put signal in at the 'Power Amp In' jack?

Yes, once when it happend I quickly took guitar cable out of the front and placed it in to "Power Amp In" jack and it was also dead. So the whole amp is affected, yes. When the sound comes back all inputs work good again, everything perfect, and than all over again... The only thing not effected is heaters and pilot lites.

[Emetal]

The damn problem will not happend at a bedroom level, I have to be playing at a rehearsel level with a volume a bit over 2.

[Emetal]

Before you go replacing those parts, monitor your B+ see if it drops out when you have the symptoms. Relay 5 and TS9 are part of a delay turn on circuit that switches B+ to the amp. So, see if you still have B+ after the relay when the amp cuts out.

I will, but I have to take it to a rehearsal space again since the problem does not manifest itself at a bedroom levels, seems that I have to be playing with a volume level just a bit over 2. Which is loud for home :-/

[Jon Snell]

You have checked the send return connectors and the connecting cables within the amplifier, they are reknown to give issues as the contacts heat and expand. Give them a wiggle and your issue will most likely dissapear.

[Emetal]

You have checked the send return connectors and the connecting cables within the amplifier, they are reknown to give issues as the contacts heat and expand. Give them a wiggle and your issue will most likely dissapear.

I am using preamp out - power amp in loop all the time since I have Delay and solo boost in there. This amp has several other send return loops but they are all WITHIN preamp section as I can see, they would not influence the power amp section right? In my case power amp section goes dead TOO when this happens. I will wiggle everything but it all seems tight.. The biggest problem for me is to recreate the issue, then it would be much easier to trouble shoot

[g1]

Do you have a load resistor you can use instead of a speaker?

[Emetal]

Played at home for two and a half hours, heated the amp with the hairdryer, knocked everything with wooden stick, wiggled and shook, voltmeter hooked on B+ for monitoring and nothing happend. Seems that amp must be played at higher volume for this to happen. I will do that over the weekend and post update. In a mean time any guesses are welcome.

[Emetal]

Do you have a load resistor you can use instead of a speaker?

No I don't, I use speaker, why? What you have in mind? You mean to crank it up at home without attracting police :-) I will check if I can obtain one here in Serbia, but I will take the amp to a rehearshel space over the weekend and crank it anyway..

[Jon Snell]

This is what I have used for many years. I can crank a large amplifier up and I get a pleasing 2Watts of power.

[Emetal]

This is what I have used for many years. I can crank a large amplifier up and I get a pleasing 2Watts of power.

Overhere I can not find 8 OHms 100 Watt resistor but they have 8,2 Ohms 50 Watt, maybe that should be OK? I do not have to crank more then 2, or 3 on the volume. Very usefull gadget :-) will make one definitely. Thanks.

[Emetal]

This is what I have used for many years. I can crank a large amplifier up and I get a pleasing 2Watts of power.

If the speaker is 8 Ohms and resistor is 8 Ohms, then total load of this gadget is 4 Ohms right?

[Helmholtz]

The series lamp acts as a compressor. Its resistance increases with applied voltage.
With 12V across the lamp, its nominal resistance is 66R. At low voltage its resistance might be only 10R.
So total load impedance may roughly vary between 6R and 7R.

Problem is that at 100W output the 12V lamp voltage will be considerably exceeded.
Maybe two 12V lamps in series?