Search found 16 matches

by upunkt
Sat Jul 18, 2020 1:55 pm
Forum: HELP!
Topic: Vermona Synthesizer: Keyboard maintenance and calibration
Replies: 1
Views: 1781

Re: Vermona Synthesizer: Keyboard maintenance and calibration

Hi, I've been owning and servicing both a Vermona E-Piano and the Vermona Piano-Strings (still own the piano), both instruments seem to make use of the same technique as the Vermona Synthesizer regarding key/voltage flow. I had the impression that these bars are covered with silver. However, to get ...
by upunkt
Sat Jul 18, 2020 1:35 pm
Forum: HELP!
Topic: TR-707 LCD Repair
Replies: 4
Views: 3542

Re: TR-707 LCD Repair

I own a 707 that also lacks display information sometimes. I haven't found the time to get it sorted but I assume it's a broken path on one of the boards since the display can be triggered to show information by pressing a finger on a certain spot of the housing. I've had a couple of broken paths fi...
by upunkt
Tue Apr 28, 2020 9:55 pm
Forum: HELP!
Topic: Juno 60 stiff sliders
Replies: 2
Views: 2248

Re: Juno 60 stiff sliders

I have had stiff slider issues on my Juno-6 and it turned out to be dust acquired over many many years. The stiffness lead to another issue, by using such a slider with some force a metal part inside got loose and twisted resulting in sliders that could not be moved over the whole range. While I was...
by upunkt
Tue Apr 28, 2020 9:40 pm
Forum: HELP!
Topic: Yamaha dx100 blank display
Replies: 2
Views: 1821

Re: Yamaha dx100 blank display

I don't know a DX100 from inside but since it has a lot in common with a DX27 which I owned and repaired I suggest double checking display connections. On my DX27 the ribbon cable had come loose on 2 or 3 pins resulting in no information on the display on startup. Depending on which lines are cut yo...
by upunkt
Mon Jul 29, 2019 3:21 pm
Forum: HELP!
Topic: Yamaha DX7 - Need help fixing loud crackling noise
Replies: 2
Views: 3677

Re: Yamaha DX7 - Need help fixing loud crackling noise

This is static noise. Could be the result of a leaking capacitor that is accidentally connecting paths on a board. Look at the PCBs, you will spot leaked elekrolyte easily. Then you'd have to clean thoroughly and replace the cap(s) in question. Cleaning can be done e.g. with (distilled) water, soap ...
by upunkt
Sun Mar 24, 2019 2:09 pm
Forum: HELP!
Topic: Roland TR-707 Germanium Diode Replacement
Replies: 5
Views: 2656

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: 2656

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: 2656

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: 4028

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: 4028

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: 4028

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: 3216

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: 4028

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: 5486

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: 4028

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 ...