Niko Bakulich
New member
- Joined
- Apr 5, 2023
- Messages
- 1
Hi all!
Long-time lurker, first-time poster. Hoping for some advice troubleshooting this very funky (if a bit mysterious) Japanese delay unit. I can't seem to track down any schematics online for this thing, so if anyone has a lead on some it would probably make the process significantly easier.
The background is that I bought this from a local producer in a non-functional state. When I opened it it had all the original capacitors but the NPN transistors had been shotgun replaced by KSC1845s through the whole thing. I replaced all the electrolytics bigger than 1uf and replaced the many little 1uf BP caps with film equivalents. Since this was designed to run on 100V (according to the back panel) I also added 25% to all the voltage values in the power section. I put a three-prong cable on to replace the brittle lamp cord it had originally.
It also came with the bag of original transistors which consist of 8 C1815s and 4 C1681s. Not totally sure where the 1861s originally went on the PCB; there aren't any markings to indicate.
After the recap, the unit passes signal but output is very very low. It looks like all the (unobtainable) BBD ICs are intact and functional, thankfully, but something in the delay path is losing a ton of signal. When sending signal through the dry path, signal loss is minimal. Voltages are steady on the board, looks like there's a +/- 20V rail and a 12V rail.
My basic questions is: Was the transistor substitution appropriate or could it have led to this signal loss? Looking at the datasheets, the only thing that sticks out to me is that the C1815s can drive 150ma of current while the newer KSC1845s are only rated for 50ma. I'm certainly not an expert, however, and appreciate a practiced eye on it.
If the transistor sub wasn't the problem, anyone have any suggestions where to start troubleshooting the output loss? I'm including photos of the pcb here and any suggestion would be super valuable.
Long-time lurker, first-time poster. Hoping for some advice troubleshooting this very funky (if a bit mysterious) Japanese delay unit. I can't seem to track down any schematics online for this thing, so if anyone has a lead on some it would probably make the process significantly easier.
The background is that I bought this from a local producer in a non-functional state. When I opened it it had all the original capacitors but the NPN transistors had been shotgun replaced by KSC1845s through the whole thing. I replaced all the electrolytics bigger than 1uf and replaced the many little 1uf BP caps with film equivalents. Since this was designed to run on 100V (according to the back panel) I also added 25% to all the voltage values in the power section. I put a three-prong cable on to replace the brittle lamp cord it had originally.
It also came with the bag of original transistors which consist of 8 C1815s and 4 C1681s. Not totally sure where the 1861s originally went on the PCB; there aren't any markings to indicate.
After the recap, the unit passes signal but output is very very low. It looks like all the (unobtainable) BBD ICs are intact and functional, thankfully, but something in the delay path is losing a ton of signal. When sending signal through the dry path, signal loss is minimal. Voltages are steady on the board, looks like there's a +/- 20V rail and a 12V rail.
My basic questions is: Was the transistor substitution appropriate or could it have led to this signal loss? Looking at the datasheets, the only thing that sticks out to me is that the C1815s can drive 150ma of current while the newer KSC1845s are only rated for 50ma. I'm certainly not an expert, however, and appreciate a practiced eye on it.
If the transistor sub wasn't the problem, anyone have any suggestions where to start troubleshooting the output loss? I'm including photos of the pcb here and any suggestion would be super valuable.
