Would a tip120 replace the 78005AP 5v positive voltage regulator?
- Thread starter sameal
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Help Support GroupDIY Audio Forum:
I was just looking at 7805. I searched for the device instead of a list of equivelents. Probably a better way to find them.
I was having power cycles randomly, now the main board is totally dead, but the lfo button comes on. No audio.
I have a little china tester for transistors, but i feel like it doesn't really tell much. I need a cricket or something.
Just gonna take a stab at the transistors being the issue i suppose.
I was having power cycles randomly, now the main board is totally dead, but the lfo button comes on. No audio.
I have a little china tester for transistors, but i feel like it doesn't really tell much. I need a cricket or something.
Just gonna take a stab at the transistors being the issue i suppose.
For those who don't know, the "JX-3p" is a fairly sophisticated keyboard synthesizer.
I don't know that "take a stab" is the best path. Documentation and brain-work is another way to go.
I don't know that "take a stab" is the best path. Documentation and brain-work is another way to go.
Well, i'm picking up this project again after ripping my hair out a few years ago with it.
I had measured good voltage, but the keyboard kept power cycling randomly. At that point i had much less test equipment, and decided to recap the power supply. That didn't work.
So then, i wiggled connectors, searched for cracks in traces, reflowed weak looking solder joints, nothing worked.
Transistors is the last thing i could probably do on my own at this point. After that it's back on the shelf.
I'm going to check volts again, and test the caps since it's been a few years. I do have an o-scope, but im not well versed in it yet.
The only thing that "supposedly" happened was shipping damage. I got this synth second hand from someone who purchased it on ebay "fully working" but when it arrived, several keys were broken where a hole in the box was. When it was powered on, the random power cycling happen, and has happened until two days ago when the front panel minus the lfo button went completely dead.
I checked in the damage area for cracked traces, and also found nothing.
I had measured good voltage, but the keyboard kept power cycling randomly. At that point i had much less test equipment, and decided to recap the power supply. That didn't work.
So then, i wiggled connectors, searched for cracks in traces, reflowed weak looking solder joints, nothing worked.
Transistors is the last thing i could probably do on my own at this point. After that it's back on the shelf.
I'm going to check volts again, and test the caps since it's been a few years. I do have an o-scope, but im not well versed in it yet.
The only thing that "supposedly" happened was shipping damage. I got this synth second hand from someone who purchased it on ebay "fully working" but when it arrived, several keys were broken where a hole in the box was. When it was powered on, the random power cycling happen, and has happened until two days ago when the front panel minus the lfo button went completely dead.
I checked in the damage area for cracked traces, and also found nothing.
As this is the only thread I found about the Roland JX 3P , I write here as I have one here on my table that has problems on 2 of 6 voices..
The synth gave me some headaches …
I already recapped the whole unit and found a rotten trace on channel/voice 6
That one was completely dead through this and now works perfectly.
The problems still present are on channel 1-2 for dco2 and on 1 of dco1. (you can hear the voices on a very low level means they actually work)
So the behavior is .. you switch on the unit… All voices WORK and then… the problem voices get faded out slowly.. and remain on a very low level..
With the scope there is a saw signal on IC104 pin 1 and 6 first and then gets flat slowly .. but this saw should stay stable (seen on the ICs of the other channels/voices)
It‘s like water that runs out slowly…
All is built discrete..
I already replaced the transistors around IC104 (op amp) and the op amp itself, but that did not help.
There are caps around the op amp, but when checked, they were aright…
Has someone experience with that synth? Is this a common known issue on it?
Anything else seems to work fine
Thanks!
Edit: Solved! I found out, the multiplexer ICs had a problem. Can‘t exactly tell what, but I exchanged IC 28 (4051) that is connected to the opamps to for Dco 1 and 2 and the voices were back loud and clear..
Also exchanged the other 4051 Ics 23, 26, 27 (connected to the opamps for VCA and VCF) just to be sure to avoid problems by them in the future.
The synth gave me some headaches …
I already recapped the whole unit and found a rotten trace on channel/voice 6
That one was completely dead through this and now works perfectly.
The problems still present are on channel 1-2 for dco2 and on 1 of dco1. (you can hear the voices on a very low level means they actually work)
So the behavior is .. you switch on the unit… All voices WORK and then… the problem voices get faded out slowly.. and remain on a very low level..
With the scope there is a saw signal on IC104 pin 1 and 6 first and then gets flat slowly .. but this saw should stay stable (seen on the ICs of the other channels/voices)
It‘s like water that runs out slowly…
All is built discrete..
I already replaced the transistors around IC104 (op amp) and the op amp itself, but that did not help.
There are caps around the op amp, but when checked, they were aright…
Has someone experience with that synth? Is this a common known issue on it?
Anything else seems to work fine
Thanks!
Edit: Solved! I found out, the multiplexer ICs had a problem. Can‘t exactly tell what, but I exchanged IC 28 (4051) that is connected to the opamps to for Dco 1 and 2 and the voices were back loud and clear..
Also exchanged the other 4051 Ics 23, 26, 27 (connected to the opamps for VCA and VCF) just to be sure to avoid problems by them in the future.
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