Search found 11 matches

by upunkt
Sun Mar 24, 2019 2:09 pm
Forum: HELP!
Topic: Roland TR-707 Germanium Diode Replacement
Replies: 5
Views: 1141

Re: Roland TR-707 Germanium Diode Replacement

I tried both AA113 and AA143. Both Ge diodes let the ride cymbal decay smoothly, while the ride volume level was also affected and dropped. Sound was not affected. AA113: decay a bit too fast but very soft in the end, volume slightly lower than the crash volume AA143: smooth decay as long as the sam...
by upunkt
Wed Mar 13, 2019 10:35 pm
Forum: HELP!
Topic: Roland TR-707 Germanium Diode Replacement
Replies: 5
Views: 1141

Re: Roland TR-707 Germanium Diode Replacement

VCA modulation! This sounds very reasonable, thanks. I checked specs for 1N34a and could not find the 0.3 V drop. What I found is that depending on the manufacturer the diode characteristics vary in a certain range. What I can get very easy is an AA143 (from DSI) which claims to have a VF of about 0...
by upunkt
Mon Mar 11, 2019 9:35 am
Forum: HELP!
Topic: Roland TR-707 Germanium Diode Replacement
Replies: 5
Views: 1141

Roland TR-707 Germanium Diode Replacement

I'm currently refurbishing a Roland TR-707 Drum Computer. One of the issues is a broken diode, D17. In the service manual it's described as "Ge Di" which probably translates to Germanium Diode. Unfortunately, no other information about the diode is available. In the SM it's written that one could re...
by upunkt
Sun Oct 28, 2018 5:34 pm
Forum: HELP!
Topic: Korg LP-10 LP10 problem: all sound distorted
Replies: 8
Views: 2610

Re: Korg LP-10 LP10 problem: all sound distorted

Just for the record: The LP-10 works again. I did two things, finally. I substituted the voltage regulator NEC μPC14312 with an ST L7812. This resulted in a nearly clean signal, also much louder than before. Since it was not 100% perfect I doublechecked all steps I'd done before. I found two caps th...
by upunkt
Wed Oct 17, 2018 12:31 am
Forum: HELP!
Topic: Korg LP-10 LP10 problem: all sound distorted
Replies: 8
Views: 2610

Re: Korg LP-10 LP10 problem: all sound distorted

I can get an ST L7812 at a local store. Schematics and specs look pretty much the same as NEC μ PC14312 which seems to be fixed voltage regulator, and pins in same order. I'll give that a go, after further measurement. Thanks a lot for your input so far.
by upunkt
Tue Oct 16, 2018 11:46 pm
Forum: HELP!
Topic: Korg LP-10 LP10 problem: all sound distorted
Replies: 8
Views: 2610

Re: Korg LP-10 LP10 problem: all sound distorted

Thanks, yeah will check that.
by upunkt
Tue Oct 16, 2018 11:45 pm
Forum: HELP!
Topic: D-50 Part
Replies: 8
Views: 2150

Re: D-50 Part

You can use basically any flat plastic like cheese packaging or likewise cut to stripes. Make sure to attach the stripes properly with doublesided tape, gaffa or sth similar.
by upunkt
Tue Oct 16, 2018 10:11 pm
Forum: HELP!
Topic: Korg LP-10 LP10 problem: all sound distorted
Replies: 8
Views: 2610

Re: Korg LP-10 LP10 problem: all sound distorted

Ah, thanks, this is the kind of reply I like, with technical detail that I could not come up with. I did not measure voltage nor ripple before I set the transformer to 240 V. Just looked at the transformer and was sure it could be set to be used with different voltages so this was just the first thi...
by upunkt
Tue Oct 16, 2018 4:25 pm
Forum: Gear Services & Other Goods
Topic: do not answer here please
Replies: 2
Views: 4153

Re: Korg LP-10 LP10 problem: all sound distorted

Thanks, moved the question there.
by upunkt
Tue Oct 16, 2018 4:23 pm
Forum: HELP!
Topic: Korg LP-10 LP10 problem: all sound distorted
Replies: 8
Views: 2610

Korg LP-10 LP10 problem: all sound distorted

Hi! I got a KORG LP-10 recently found in a barn outside of Berlin in former East Germany, dirty, rotten and completely out of function. I managed to get it back to work. Unfortunately, all sound is a bit low in level and distorted. Both built-in speakers are in good shape and technically ok, btw. I ...
by upunkt
Sat Oct 13, 2018 4:08 pm
Forum: Gear Services & Other Goods
Topic: do not answer here please
Replies: 2
Views: 4153

do not answer here please

Question moved to viewtopic.php?f=5&t=106208