Laney L5T intermittent loss of volume

[LazyDave]

I have a Laney L5T amp. I can play for 30 mins or so then suddenly lose all volume. I still get the sound through the reverb path and I can plug guitar into the send or return jacks and get sound out. Changing the reverb changes the volume. After some time or some random plugging in and out the normal full sound returns. Drive and bright switches have no impact on the issue. Any help would be appreciated. I have access to the schematic..
thanks
Dave

[g1]

schematic attached.
Have you tried it with a patch cable installed between send and return?

[LazyDave]

Thanks G1. I had removed R28 as per a common mod for making the effects loop serial rather than parallel. Part of the mod. puts a link wire across the send /return socket that is then broken when a pedal is plugged in. Its worked for over a year...although as it happened I never had cause to use the loop. When it started to behave erratically - I tried a link cable expecting that to sort it as you suggest but it didn't do.....turns out I had put the jack mounting pcb upside down meaning I was bridging the Return with the reverb/drive foot-switch socket :-(. Having identified that, I have resoldered the wire link and put the jack board the right way up. The issue has not been solved but putting a patch cable across the send - return when it happens does resolve the issue.

It suggests just a dirty contact in the send or return socket ? Something else ?

[g1]

Yes, it suggests the return jack has dirty/oxidized contacts or is defective (or bad solder joints).
Not clear on the mod, as far as what the link does.

edit: Ok, I see that it does not have the usual connection from send tip to return switch contact, so that is where the added link goes.

[LazyDave]

You got it- re the mod. I have sprayed some contact cleaner in the jack sockets and tried to ensure a good spread by plugging a jack in and out. All seam well now but if it recurs I will dismantle and give a good clean with tips etc.

BTW how are lane for supplying spurs ie a replacement for the small pc board or replacement jack socket etc ?

[mikeydee77]

I reckon those black springy cliff connectors (Marshall, Laney, TraceElliot and many others) have a good lifetime of about 10y and then start becoming unreliable definitely by about 15y. I imagine a combination of oxidisation and fatigue and abuse. I generally replace the ones with a switching or interrupting role after they get old e.g headphones, FX return and inputs.

Headstock Distribution are Laney in the UK. I occasionally buy parts from them and they are pertty helpful. Not sure if they are happy dealing with general public but independent techs no problem.

[LazyDave]

Doh...it happened again. When in fault mode, putting a patch cable across the Send/Return has no effect. Turning the reverb off results in no signal, tuning it to max gives all wet signal but no dry signal. Playing guitar through either the send or return jack does work. turning on the drive channel and treb, middle, bass all effect the wet signal as expected.

There's no guaranteed way to fix it but putting the volume on max then bringing it down had the desired effect today.

This suggests to me that the problem is not with the send/return jacks although I will disassemble and clean properly.

Any further thoughts ?

[g1]

When in fault mode, putting a patch cable across the Send/Return has no effect.
...
Playing guitar through either the send or return jack does work

This seems to leave only R14 or the HD1 connector to the FX jack board. Most likely a solder problem related to those parts, or oxidized connector.

[LazyDave]

Thanks G1. Touch wood - have cleaned the jack switches properly after disassembly and am waiting for next recurrence. If it happens again will reflow the solder around the jacks and the R14. Alternatively might remove the mod and replace R28 smd

[LazyDave]

Latest episode. Usual issue. Turning the volume up saw some of the signal getting through. Plugging and unplugging a jack into the send returned normal operation.

[g1]

Can you post some photos of the FX loop jacks on both sides of board, including mods.