- Forums
- »
- Technics Instruments Repairs
- »
- PR603M in need of service repair manual....NO SOUNDS!
|
Viewing 1 to 11 (11 Total) PR603M in need of service repair manual....NO SOUNDS! |
|
|---|---|
Bolinky
United States Total Posts: 8
Joined: February 28, 2017
|
PR603M works fine other then no sound from internal speakers. I can turn the main volume to max and you can hear it coming through very low and scratchy. Headphones and line out works fine however. I also managed to test the speakers outputs with a multimeter and found DC voltage around 3 to 4 volts. I changed out the speakers with new ones and no luck just the same very low hard to hear at max volume with a cutting out scratchy sound. Hope that someone can help or has a repair manual to offer. I need to know what circuits to change out and with out a repair manual its not easy. Any body?
Tags:
sound problem, volume issues, pr603m, no sound, scratchy, cuts out, PR603M, service repair manual, low volume
Posted on February 28, 2017 at 4:53 AM
|
|
|
|
davetutt
United Kingdom Total Posts: 166
Joined: January 12, 2015
|
Re: PR603M in need of service repair manual....NO SOUNDS!There should be no DC volts on the speaker connections. This suggests that the power amp may have failed. This isn't exactly a straight forward repair as this is early class D output stage hence its small size and the very small heat sink. I would suggest that as a first move the 4 output mosfets on the left hand heat sink be swapped out. There are no circuit protection components on this particular model other than some dedicated special resistors on the small driver board so it is unlikely that there has been any serious failure whilst the piano is running. The small upright board contains the comparator and driver system for the switching which, given the DC on the output would seem to indicate the output has latched up.
Posted on February 28, 2017 at 9:36 AM
|
Bolinky
United States Total Posts: 8
Joined: February 28, 2017
|
Re: PR603M in need of service repair manual....NO SOUNDS!Here is a pic of the board and the small heatsink has only two mosfets. Please see attached files. I've looked these boards over for cold solders or fractures of any kind and I find nothing. If you need to see or know anything else please ask...I beg of you?
Attachments:
1488291371527-137593678.jpg
1488291506079-1310944954.jpg
Posted on February 28, 2017 at 2:21 PM
|
Bolinky
United States Total Posts: 8
Joined: February 28, 2017
|
Re: PR603M in need of service repair manual....NO SOUNDS!Here in these pics I have noticed on this larger heatsink that does have 4 mosfets the third one is reading ohms while all other mosfets including the two on the smaller heatsink read nothing. Does that indicate that the third mosfets is bad and my only problem perhaps? ?
Attachments:
14882923088371244069326.jpg
14882923448661203985195.jpg
Posted on February 28, 2017 at 2:39 PM
|
davetutt
United Kingdom Total Posts: 166
Joined: January 12, 2015
|
Re: PR603M in need of service repair manual....NO SOUNDS!I would replace the whole lot as if there is one that is different the others may well be stressed.
Posted on March 3, 2017 at 7:36 PM
|
davetutt
United Kingdom Total Posts: 166
Joined: January 12, 2015
|
Re: PR603M in need of service repair manual....NO SOUNDS!Also, on the plug in driver board there are 4 transistors here that should be replaced. These as the driver pairs directly above J321 and 322
Posted on March 3, 2017 at 7:40 PM
|
Bolinky
United States Total Posts: 8
Joined: February 28, 2017
|
Re: PR603M in need of service repair manual....NO SOUNDS!Thanks for all your help. I purchased all replacements you recommended for this project and I also pulled out the 4 heatsink mosfets to pull a true diode test, 3 of 4 had failed. It will be three weeks before all the chips get here from Asia so it could be a bit before I post a follow up on the repairs. I do have a question as to how do I find an upgraded replacement transistor instead of the original transistor? I know that it can be Cross referenced and I did find some cheaper ones but how do I know if it is truly better than the original? Buying all the originals cost me $100 vs had I bought cross referenced parts that are cheaper and available in my home state for $20. Shouldn't newer current chips outperform the original outdated ones?
Posted on March 4, 2017 at 7:45 AM
|
admin
United Kingdom Total Posts: 1055
Joined: February 2, 2014
|
Re: PR603M in need of service repair manual....NO SOUNDS!Bolinky and Dave,
Posted on March 5, 2017 at 10:27 AM
|
Bolinky
United States Total Posts: 8
Joined: February 28, 2017
|
Re: PR603M in need of service repair manual....NO SOUNDS!Thank you for adding the service manual Admin it is truly a blessing to have!
Posted on March 9, 2017 at 6:25 PM
|
Bolinky
United States Total Posts: 8
Joined: February 28, 2017
|
Re: PR603M in need of service repair manual....NO SOUNDS!Update on Repairs: I haven't received replacement parts as of yet but I repaired the pedal cord. Here attached are photos of a diagram I used to make it. The pedal side connector I decided to just solder strait to the board since I had no connector.
Posted on March 9, 2017 at 6:36 PM
|
Bolinky
United States Total Posts: 8
Joined: February 28, 2017
|
Re: PR603M in need of service repair manual....NO SOUNDS!I replaced all 4 mosfet transistors and the 4 on the upper driver board and no fix. I'm getting 0.25 volts on speaker sub outputs. I noticed the large heatsink with the new transistors does not get hot and remains cold to touch. Small heatsink does get hot. Line out and headphones work. I can hear a very very low amount of sound when at max volume through the internal sub speakers that has a horrible scratchy cutting in and out sound. The problem remains and I'm not sure where to look next, please help!
Posted on March 14, 2017 at 3:29 AM
|