Hi everybody,
I am the proud owner of a Denon PMA-560 that my father gave to me a few years ago. Sadly, the sound coming out of the speakers recently started to deteriorate. First in the right channel, then in both. The sound is randomly coming out more or less clean. Sometimes, there is barely any sound coming out...
I have not been able to attribute the issue to a specific input ou output channel. It keeps coming back no matter the source (turntable/PC), the input or the output. I already tried cleaning the output switch as it was tripping (same issue as in this thread) but the problem persists. All of this led me to think that there is a faulty electronic component that I should replace.
Ther person behind this great website helped me and it seems that the output relays could be responsible (specs are : HEC DHT2TU type, 24VDC, 3A120V AC). I don't know which relay I should buy to replace them.
Should I look for the same specs ? If yes should it be a coil tension of 24V ~120V AC or DC ?
Could I kill two birds with one stone and chose some better ones to make an upgrade ? If yes which ones ?
Thanks for taking the time to read this !
I am the proud owner of a Denon PMA-560 that my father gave to me a few years ago. Sadly, the sound coming out of the speakers recently started to deteriorate. First in the right channel, then in both. The sound is randomly coming out more or less clean. Sometimes, there is barely any sound coming out...
I have not been able to attribute the issue to a specific input ou output channel. It keeps coming back no matter the source (turntable/PC), the input or the output. I already tried cleaning the output switch as it was tripping (same issue as in this thread) but the problem persists. All of this led me to think that there is a faulty electronic component that I should replace.
Ther person behind this great website helped me and it seems that the output relays could be responsible (specs are : HEC DHT2TU type, 24VDC, 3A120V AC). I don't know which relay I should buy to replace them.
Should I look for the same specs ? If yes should it be a coil tension of 24V ~120V AC or DC ?
Could I kill two birds with one stone and chose some better ones to make an upgrade ? If yes which ones ?
Thanks for taking the time to read this !
You have to refer to the schematic.The relays are RL601 and RL602, with description DH2TU.
They may be 24V coils, since there are series resistors on the coils and a 50V rail.
Look at the relays for the mfr name and part number. You have to get relays that fit the board properly.
https://www.pma560.com/pma560_service_manual.pdf
They may be 24V coils, since there are series resistors on the coils and a 50V rail.
Look at the relays for the mfr name and part number. You have to get relays that fit the board properly.
https://www.pma560.com/pma560_service_manual.pdf
The correct part is a DEC DH2TU, 1100Ω 24VDC coil, cross-bar twin contact, rated 3A@120VAC.
https://www.j-dec.co.jp/files/libs/713/202501090911052566.pdf
Thanks for the details, I made a typo, sorry about that !
I still struggle to find a matching component on the retailer website. When I enter the search filters 3A, 120VAC the results I get are relays with more than 6 pins that won't fit the PCB. Also I only get C form relays and from what i read on the pdf chrisng linked, the DH2TU is a 2a contact configuration. What am I doing wrong ?
Also i can't find any DEC parts, even when looking for Daiichi Electric Co. are they still available for sale ?
Maybe I should browse another website, I never shopped for electrical components before so I don't really know where to go. For now, I am searching on this website.
I still struggle to find a matching component on the retailer website. When I enter the search filters 3A, 120VAC the results I get are relays with more than 6 pins that won't fit the PCB. Also I only get C form relays and from what i read on the pdf chrisng linked, the DH2TU is a 2a contact configuration. What am I doing wrong ?
Also i can't find any DEC parts, even when looking for Daiichi Electric Co. are they still available for sale ?
Maybe I should browse another website, I never shopped for electrical components before so I don't really know where to go. For now, I am searching on this website.
I saw a video and description of a guy prying open such relays using nails with broad heads. I think he cleaned contact points using strips of cardboard with some cleaning fluid. Try searching "repair speaker relays"?
Cheers!
Btw. He didn't unsolder relays. He just fixed them "in situ"
Cheers!
Btw. He didn't unsolder relays. He just fixed them "in situ"
Hi Guerrilla,
Thanks for the idea. I think I found the video.
I openend the amp, took the relays caps off and tried cleaning as explained in the video.
Problem is still here. sound is unclear with clakering especially in the highs.
Here are some photos of the relays with close up on the contacts. I am far from being an expert but they seem pretty clean to me, especially considering the dust in the rest of the amp...
Thanks for the idea. I think I found the video.
I openend the amp, took the relays caps off and tried cleaning as explained in the video.
Problem is still here. sound is unclear with clakering especially in the highs.
Here are some photos of the relays with close up on the contacts. I am far from being an expert but they seem pretty clean to me, especially considering the dust in the rest of the amp...
To find a matching relay, search for 24VDC 1100Ω coil, 2 Form A contacts and through hole solder pins. For contact ratings, it's fine if it's 3A or higher.
I searched Mouser for general purpose relays and found 7 matching.
https://www.mouser.com/general-purpose-relays/?
Just 120V 3A is not nearly good enough. You have to fully qualify the relay. There are many many types of relays.
You also must be certain that it properly fits on the board. There are many different footprints, and you'll have to measure the layout and pins.
Have you checked that the relays haven't vibrated loose their solder? It's not uncommon for PCB mounted relays, switches, potmeters and transformers that the solder goes loose after many years.
If Denon made the same mistake as Technics in the SU-VZ320, the reverse voltage rating of the freewheeling diodes across the relay coils may be inadequate, see https://www.diyaudio.com/community/threads/design-errors-in-commercial-equipment.396887/post-7293642 . That can also cause problems after many years.
Edit: I just checked the service manual rayma linked to, and Denon did not make the mistake Technics made. The freewheeling diodes D605...D607 are of the type 1SS270A, which can handle 60 V continuous reverse voltage and 70 V peak. That should work fine with 50 V supplies.
If Denon made the same mistake as Technics in the SU-VZ320, the reverse voltage rating of the freewheeling diodes across the relay coils may be inadequate, see https://www.diyaudio.com/community/threads/design-errors-in-commercial-equipment.396887/post-7293642 . That can also cause problems after many years.
Edit: I just checked the service manual rayma linked to, and Denon did not make the mistake Technics made. The freewheeling diodes D605...D607 are of the type 1SS270A, which can handle 60 V continuous reverse voltage and 70 V peak. That should work fine with 50 V supplies.
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