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Marantz 170dc help/advice/guidance Need help after my mistake!

Richs_Trains

Richs_Trains

Well-Known Member
Hey all,

The 140 turned out well with all the help on AK, a few hiccups, but all is good. I also have a 170dc that I would like to refresh. I started with PN00 and replaced the electrolytic caps, I had the exact replacements for all except CN04, which is a 10uf 63v. I put a 10uf 100v in its place and now I no longer have a right channel and the left is not as clear as when I started. All I changed were the electrolytic caps on the board and every one was value for value except CN04. I am thinking it's the relay because when I tap on it the left channel changes, but the right channel is still out. I have the 10uf 63v on order although I was under the impression you could increase the voltage on a cap without affecting its intended function. What I would like to know is what is the proper modern replacement for the relay on a 170dc. Thank you very much, Rich
 
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In searching around AK, I found that the MY4-02-DC24 is the suggested replacement for an MS4U 24v relay, am I right in this?
 
Richs_Trains said:
...I had the exact replacements for all except CN04, which is a 10uf 63v. I put a 10uf 100v in its place and now I no longer have a right channel and the left is not as clear as when I started...
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The loss of output in the left channel is unrelated to CN04. The CN04 capacitor just filters the raw DC on the PN00 board; the 10µF/100V replacement is fine (IIRC, I installed a 33µF/63V in mine).
 
Richs_Trains said:
In searching around AK, I found that the MY4-02-DC24 is the suggested replacement for an MS4U 24v relay, am I right in this?
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Yes, the Omron MY4-02-DC24 is a suitable drop-in replacement (once the 4 pins at the front of the relay are clipped off).
 
Leestereo said:
Yes, the Omron MY4-02-DC24 is a suitable drop-in replacement (once the 4 pins at the front of the relay are clipped off).
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Thank you for the reply Leestereo, hopefully, the relay is my problem. I really don't see much else that would affect the audio on that board, it looks like audio comes in directly from P-700 and goes out to the speaker terminals. I thought I read somewhere about a capacitor controlling the timing of a speaker relay, the SM shows it as a 10uf 50v on the schematic and a 10uf 63v in the parts list. What was the reason you went to a 33uf in your rebuild? Thanks, Rich
 
CN04 is only filtering DC (increasing CN04 reduces the AC ripple in the circuit). The 220µF CN05 capacitor is for the relay timing.
 
Leestereo said:
The 220µF CN05 capacitor is for the relay timing.
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Thank you again for your information, Leestereo. The only way I learn is when the great people on AK explain it to me in simple, direct terms! I will look at the schematic and see if I can follow the 220uf connection to the relay. Rich
 
Leestereo said:
Yes, the Omron MY4-02-DC24 is a suitable drop-in replacement
Click to expand...
Just wondering, the Omron is only rated at 3a and the MS4U is rated at 7a, will this be a problem? I have a couple of stock 4400 relays which are 48v and have a higher amp rating, would these be a better solution? Thanks, Rich
 
Relay came today, installed it, and have both channels back. Will be doing each power amp and then the filter caps. Thank you for your help. Rich
 
So, re-capped the left amp and was putting new mica and compound on the outputs when I ran out of heat sink compound, can't test, back when it comes in. Rich
 
Ordered some DOW 340 compound, now I have enough for the rest of my life. New thermal compound and mica insulators on transistors and re-capped both amps. Cleaned connecting pins and she's good to go. The old mica insulators were fused to the heat sinks and had to scrape them off, so I guess they needed to be changed. Put warm white LED's in the meters, the original lamps were all still working, but the LED's are so much cooler running. Next up, changing out the dual cap which looks a little daunting and will require an attack plan before I attempt it. Thanks for all the help. Rich

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Well, I can't seem to do anything without a little drama. I laid everything out the way I wanted it, drilled my holes, and mounted the filter cap "package". Followed my little diagram and made all the underside connections. Everything looked great, but my mind wasn't really working because when I flipped the switch on my DBT, I got bright light. Uh oh, I don't know what I was thinking, I looked at that stripe on the filter cap and my mind said positive when I know the stripe side is negative. I wired the whole package in backward, thank goodness for the DBT. I removed all my connections (what a pain) and had to rotate each cap 180 degrees, then re-mount everything again. Re-made all my connections and flipped the switch and everything seemed to be working. Went to dinner and came back and turned it on again and the right channel sounds fuzzy and has no power, ugh. Since I don't have a scope, I hit some of the transistors with freeze spray, no change. Then I decided the only way I would know if it was the power amps was to switch sides and see if the problem moves. Well, I switched all the brackets around and re-mounted the power amps, flipped the switch and both channels are strong and clean. Don't know what happened, maybe a loose plug connection. Anyway, I played it about a half-hour and no issues. Put all the covers on and fired it up again, still good. Played another 15 minutes without a problem. Hope it was just a loose connection and I didn't do any damage! Will play it tomorrow and cross my fingers. Rich


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So, I finally got up the nerve to turn it on again this morning and darn if the problem wasn't back. I have low volume and static sound in the right channel. Last night I switched the power amp boards to see if the problem moved with the boards, but it did not. The problem is still in the right channel. As I mentioned before, I installed the filter caps with the wiring reversed connecting the red wire to the negative and the white to the positive of the filter cap package. The DBT caught the problem and the unit was maybe powered for 5-10 seconds. I don't know if I damaged the filter caps in this process and would like to know where I should look to solve this. The filter caps were quite expensive, but I purchased 4 as I have another 170dc and the caps were in limited supply. The unit was working fine before I changed the filter caps and made my mistake. Do the filter caps each represent a channel or do they work across both amplifiers evenly? Completely lost as to where to look, any help and guidance would be much appreciated. Rich
 
Richs_Trains said:
...Do the filter caps each represent a channel or do they work across both amplifiers evenly?...
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The power supply provides the B+ and B- DC voltage rails for both channels. A problem with the power supply would affect both channels. Have you cleaned the AC/DC input coupling switch on the back panel?
 
Leestereo said:
Have you cleaned the AC/DC input coupling switch on the back panel?
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Thank you Leestereo, Brad from Previd also recommended this and after cleaning the problem seems to be gone. Will operate it throughout the day and report back. You guys are great!! Rich
 
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