I got this amp in with a blown power supply, and many damaged traces in the power supply section. I removed all the outputs and checked them. They are all O.K.
I repaired all the damaged traces. I removed all the ps transistors. I removed and checked all the BCP53/56 drivers for both the ps and output sections.
Now here is the problem... all drivers are O.K. I reinstalled them. When I add power it goes straight into protect. LED blinks rapidly for about 16-17 flashes then tries to turn on. I get a quick look at the ps wave form which looks different from what I'm use to. It only tries to come on for a second or 2 then goes back into protection. It doesn't seem to be trying to pull excessive current. There is about 5vdc on the speaker output terminals while in protect and it goes down to about 2.5v when it tries to turn on.
Please see the pic of the wave form. The settings are 5v/div and 20us.
On the check holes next to the IC I get:
4.9vdc on VDD,
4.9vdc on VPP,
2.28vdc on CLK,
0.000v- 0.005vdc on DAT (goes up when not in protect)
0.000v- 0.005vdc on VSS (goes up when not in protect)
I'm thinking maybe the PIC16F1828 is the problem??? Is there a good way to check it? I'm not sure what pins do what. I should have much more voltage on VSS should I not?
That wave looks the same on the emitter of both BCP56N's.
I repaired all the damaged traces. I removed all the ps transistors. I removed and checked all the BCP53/56 drivers for both the ps and output sections.
Now here is the problem... all drivers are O.K. I reinstalled them. When I add power it goes straight into protect. LED blinks rapidly for about 16-17 flashes then tries to turn on. I get a quick look at the ps wave form which looks different from what I'm use to. It only tries to come on for a second or 2 then goes back into protection. It doesn't seem to be trying to pull excessive current. There is about 5vdc on the speaker output terminals while in protect and it goes down to about 2.5v when it tries to turn on.
Please see the pic of the wave form. The settings are 5v/div and 20us.
On the check holes next to the IC I get:
4.9vdc on VDD,
4.9vdc on VPP,
2.28vdc on CLK,
0.000v- 0.005vdc on DAT (goes up when not in protect)
0.000v- 0.005vdc on VSS (goes up when not in protect)
I'm thinking maybe the PIC16F1828 is the problem??? Is there a good way to check it? I'm not sure what pins do what. I should have much more voltage on VSS should I not?
That wave looks the same on the emitter of both BCP56N's.
Attachments
I can't find one specifically for that amp. Seems like the website is down too. I have a manual from a different SounDigital amp. It says 3 blinks low battery, 4 blinks low impedance. Nothing about constant flashes.
Edit: I got lucky and the owner left the manual inside the box.
After using a bunch of google translate, the only thing it says about the red LED blinking is 10 times is low power. "Red led is lit" = thermal. I'm going to put a resistor on the outputs to see if it's just cause there is no load connected just to see but I doubt it...
Adding a load made no difference and it blinks exactly 16 times, before trying to turn on, then another 16... over and over
Edit: I got lucky and the owner left the manual inside the box.
After using a bunch of google translate, the only thing it says about the red LED blinking is 10 times is low power. "Red led is lit" = thermal. I'm going to put a resistor on the outputs to see if it's just cause there is no load connected just to see but I doubt it...Adding a load made no difference and it blinks exactly 16 times, before trying to turn on, then another 16... over and over
Last edited:
I installed all the ps transistors. Now the clipping LED blinks 16 times and tries to cycle, over and over. Here is a short video (sorry Perry, I know you don't like vids but its the best way I could show whats happening). I can hear one transformer or something around it ringing a few times while it tries to start up.
http://vid1047.photobucket.com/albums/b475/deadlysones/Amp%20Repair/MVI_2775_zpssl4rdthi.mp4
http://vid1047.photobucket.com/albums/b475/deadlysones/Amp%20Repair/MVI_2775_zpssl4rdthi.mp4
The only thing Yellow blinking in the manual says it speaker shorts, impedance loads, etc. So, I went and tried to put a dummy load on the speaker terminals... I didn't think it would make any difference, with no outputs installed but I tried it.
This time when I added the remote power it made the same not quite formed wave but this time it stayed on long enough to actually form a nice square wave. Then something over by the transformer I heard ringing before (it was quiet this time) made a noise and I removed remote. Now its back to not making the wave perfectly and doing the cycling effect in the video again.
It did actually power up and make a nice square wave at one point.... I'm sure the load didn't have anything to do with it. lol I have some new drivers.... maybe I'll try to replace them. I guess if they were leaky this could happen? Either that or something with or around that one transformer I think is causing this.
This time when I added the remote power it made the same not quite formed wave but this time it stayed on long enough to actually form a nice square wave. Then something over by the transformer I heard ringing before (it was quiet this time) made a noise and I removed remote. Now its back to not making the wave perfectly and doing the cycling effect in the video again.
It did actually power up and make a nice square wave at one point.... I'm sure the load didn't have anything to do with it. lol I have some new drivers.... maybe I'll try to replace them. I guess if they were leaky this could happen? Either that or something with or around that one transformer I think is causing this.
Last edited:
Since the operation of the PIC chip isn't known, would it be possible to remove the 4427 and drive the driver transistors with an external source?
You'd need a circuit that would allow you to control the pulse width so that you wouldn't over-shoot the rail voltage. This should be easy to do with only slight modifications to a junker amp you have laying around (cheap/budget type amp would be the easiest to mod).
You'd need a circuit that would allow you to control the pulse width so that you wouldn't over-shoot the rail voltage. This should be easy to do with only slight modifications to a junker amp you have laying around (cheap/budget type amp would be the easiest to mod).
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.