NickS
Member
I've mentioned in passing my son's JCM2000 TSL100 which is an early model - all the PCBs are -00 like my JTM60. When he bought it for a fair price some years ago he wasn't aware of the issues so he gigged it. It was noisy so I recapped it with 105C caps with no significant improvement; noisy EL34s appeared to be the issue as replacement made a slight improvement.
His first gig running it in anger ended up with V8, V8's 1K 5W grid resistor, some PC track and C46 blown. Following repairs it ran OK a couple of gigs and V8/C46 went again. The temporary fix was to run it with one pair of EL34s as a 50 watter using an 8 ohm cab in the 4 ohm socket*. I did some research and found the problem with grid bias resistors and the whole drifting bias thing. I did some mods (e.g. drill out round the pin and install 5k6 resistors) which seemed to improve his bias stability issues but the thing was still somewhat noisy, so when his band was offered artiste discount by Blackstar he jumped at the opportunity and the TSL arrived in my garage.
He didn't try to sell it because he wasn't confident that it was reliable enough and he didn't want to end up with bad feedback. Forward some years and the garage needs clearing out a bit so the TSL came up on the bench.
As I came across mention of the speaker socket earthing problem on this board (while researching my JTM60 issues) I installed a jumper over the 16 ohm speaker socket earth and fired it up. The following issues are noticeable:
1. Bias control is not good enough on one side. It could be a dodgy pot but I need to double check that I replaced the NTC bias resistors.
2. After a little while the clean channel develops a hum that is not obvious on the Crunch and Lead channels.
Step 1; make sure you have a list of all the connections. I thought this might be useful to some other people too.
Please tell me if you spot any errors or if the hum is a common issue. Please don't bother telling me to replace the main board.
*Edited to correct stupidity.
Edited 8-Mar-21 to correct Clean CON6 and Lead (OD) CON1.
Edited 21-Mar-21 to remove duplicate CON1 on Rear board.
His first gig running it in anger ended up with V8, V8's 1K 5W grid resistor, some PC track and C46 blown. Following repairs it ran OK a couple of gigs and V8/C46 went again. The temporary fix was to run it with one pair of EL34s as a 50 watter using an 8 ohm cab in the 4 ohm socket*. I did some research and found the problem with grid bias resistors and the whole drifting bias thing. I did some mods (e.g. drill out round the pin and install 5k6 resistors) which seemed to improve his bias stability issues but the thing was still somewhat noisy, so when his band was offered artiste discount by Blackstar he jumped at the opportunity and the TSL arrived in my garage.
He didn't try to sell it because he wasn't confident that it was reliable enough and he didn't want to end up with bad feedback. Forward some years and the garage needs clearing out a bit so the TSL came up on the bench.
As I came across mention of the speaker socket earthing problem on this board (while researching my JTM60 issues) I installed a jumper over the 16 ohm speaker socket earth and fired it up. The following issues are noticeable:
1. Bias control is not good enough on one side. It could be a dodgy pot but I need to double check that I replaced the NTC bias resistors.
2. After a little while the clean channel develops a hum that is not obvious on the Crunch and Lead channels.
Step 1; make sure you have a list of all the connections. I thought this might be useful to some other people too.
Please tell me if you spot any errors or if the hum is a common issue. Please don't bother telling me to replace the main board.
*Edited to correct stupidity.
Edited 8-Mar-21 to correct Clean CON6 and Lead (OD) CON1.
Edited 21-Mar-21 to remove duplicate CON1 on Rear board.
Last edited:
; don't take that sheet as gospel yet.
