British made WEM ER15

[Arbutt]

Hi all
I have one of these old British made Valve amps ER15 all original never been touched
Strange fault !!
when you plug into channel 1 and turn volume up, its ok but the bass control acts weird , you have to have it about 12oclock otherwise you get no volume from that channel, Does the same on channel 2
If you use channel 1 and turn the bass on channel 2 it effects the signal from channel 1 and visa verse
Treble working correctly and causing no issues


so it looks like there is some bleed through somewhere
I have checked and swapped the tubes, Cathode bypass caps all bad so all electrolytic been changed
i was given a second one which i have now repaired and that one is working correctly
Cleaned all pots , its not an intermittent pot type fault

never really encountered this type of fault before

this amp is all original and don't really want to change components on the off chance that it might fix this fault

[Dave H]

If you use channel 1 and turn the bass on channel 2 it effects the signal from channel 1 and visa verse

Try a bypass capacitor across R6

[Arbutt]

Try a bypass capacitor across R6

Thanks Dave i will try that, But why is it the other ER15 i have don't have the same fault ?
if i do what sort of value ?
thanks Mr A

[pdf64]

Maybe C5, the decoupling cap for the preamp’s HT supply node, is bad, thereby resulting in unexpected interaction?
Is it original?

[Arbutt]

Maybe C5, the decoupling cap for the preamp’s HT supply node, is bad, thereby resulting in unexpected interaction?
Is it original?

hi PDF yes the amp is untouched still with Mullard tubes !!
I will try a new one now

[Jon Snell]

Probably a bad ground connection. Have a look near the pots.
We used to borrow them, brand new, most Friday nights from the local WEM dealer in the town and use them for our band.
Nice little amplifiers in their day.

[Arbutt]

well i have changed a few caps in the end , I believe it was V1A C8 ( pin two ) that was at fault, I'm now getting the bass control not effecting the volume level and not getting Channel 2 bass interfering with channel 1..
I'm nearly there, but both bass controls ain't doing too much, compared to the other working one .
So i think i will just replace all the non Polarized caps
i need to order some , so only time will time
many thanks for your help
Mr A

[pdf64]

Any 60s black Hunts Moldseal film caps are a safe bet to be failed / failing.

[Arbutt]

Any 60s black Hunts Moldseal film caps are a safe bet to be failed / failing.

Yes they are not brilliant on inspection . This one is really nice and untouched so i think it will do it justice to recap it
looking through my draws i seem to be really low on all values of decoupling caps , I will order when i get the go ahead from either cricklewood electronics or Hotroxs

[pdf64]

Thanks for reminding me of Cricklewood, I’ve not used them for ages.
Don’t forget about Modulus and CPC.

[Arbutt]

Cpc were cheaper, but useless with only some or none in stock. Customer wanted both er15 re capped Cricklewood were in stock, but I needed stuff from hotroxs. Got xicon type caps cheaper than mallorys

[Arbutt]

Well i have just re capped them both with all new caps all working well no bleed over from channel and tone working correctly
thanks for your help