Proton: High End Or Junk?
- Thread starter Johnny Salam
- Start date
I think i was trying to say that when using the 930 on FM it outputs both channels but plugging in a DVD player only gave one channel. Now that the DVD player is suspect i can move forward with this stereo. Its been idle for two years.
Also the R channel on the 930 is down a bunch on volume which presents another dilemma. When i plug in a new DVD player the result will be that the R channel will still be down on output unless the issue it restricted to the radio section. Also i cant plug the DVD into the D540 because its pre-amp is idle and not accepting inputs.
Repairing the 930 would be key but i have doubts about my abilities unless its a few cap replacements.
I have yet to choose a DVD player for input.
Never had this drama when all this stuff was new in 86. A new D540 and two pairs of TLX8s and a $600 entry level CD player worked a charm until the bass made the CD skip.
hornbostel
Well-Known Member
My D940 receiver has slowly developed a channel imbalance over the past few years. Its in the pre-amp section because the amp works just fine if I feed it a different source. The preamp imbalance problem comes from the volume control. At normal listening levels, there is imbalance. However, when the volume knob is rotated ~75% or more (~2-3 o'clock) the balance is fine. I haven't figured out how to service the variable gain volume knob, so I've left it alone. So now when I use the Proton D940 I have a Schiit Sys attenuator ($49) inserted between the pre-out and amp-in. I turn the volume on the D940 up to ~75% and use the Sys to control the volume. It works perfectly.
Hmm that is interesting. Thanks for your response. If i put my volume to 75% to even out the difference i would probably cause the police to knock on my door.
Most of my listening is at about 9- 10 o'clock, at 12 o'clock the floor is vibrating.
If the problem is with the variable gain volume knob, then i have read they need replacing and will not tolerate adjustment at this age. Apparently they fall to pieces when touched.
I have noticed the louder it gets the more it evens out but at my listening levels it is terrible.
I should post a pic of my ghetto speakers that are still a work in progress from 20 years ago but it might be off topic.
Time to look for threads by people who have already walked this track.
On every new (to you) amp/ receiver there are two things you should do, or when you have intermittent channel issues. First, spray all the switches, pots and dials generously with contact cleaner from the inside, followed with DeOxit Red for buttons and switches, DeOxit Green for dials and sliders. I've seen benefits from spraying the same switch three separate times in a row. Sometimes you think it's enough after one good spray and it's just not. Clean more. Then check/ adjust idle current/bias as according to the Service Manual. You have to do these things first before considering replacing anything with a channel imbalance or temporary audio dropout. If that does nothing, then start looking for anything obviously out of sorts under the hood- domed caps, burnt components/ sections of the board etc. If that looks ok, then it starts to get a little more involved, but you should at least make sure to take all the easy steps first.
Thank you for your tips AOS. I have noticed the volume switch has a slight crackle sometimes when moved. It def can use some cleaning and by your advice i will clean the pots and other switches before diving in too deep. Tracking down a service manual will probably be the most difficult task.
I noted this slight damage near the volume switch but i dont think it is my problem.
jupitersspot
Active Member
I don't think there's anything to be worried about there. Solder joint looks solid...there's just some flux that wasn't cleaned up.
Descartridge
Stereos been berry, berry good to me!
PROTON - far from junk, here's my D540
jupitersspot
Active Member
Agree with you there: I have two D540 amps, and four (I think) D940 receivers. Two of the D940s need work, but that's part of the fun.
Hey JS, ive since found the pre-amp is dodgy on the 540 (total loss R channel) and the FM circuit on the 930 is also dodgy (60% loss R channel).
So I am using the pre-amp from the 930 to push the 540 main amp. I run my input (CD/DVD) through the 930 pre-amp.
All is good atm. Using this "up time" to modify my speakers.
I like how you collect Proton amps hehe, it is quite addictive but rare to find them. (here is Aus)
One day i would like to repair these amps but if i find a good 540/940 i would simply swap it out.
jupitersspot
Active Member
It is sometimes instructive to play around with the pre-amp to diagnose it a little. Things I do:
- try different inputs. I can supply line-level inputs to CD, Tape 1, and Tape 2 and sometimes the sonic challenge is in only one input. Then you know to look at connections and switches on that input
- adjust the tone controls. Sometimes defeating tone controls (I don't recall offhand which controls are present on the D540, so forgive me if I err) -- by turning off loudness, or subsonic filters (infra-defeat), or simply twiddling the bass/treble knobs -- can eliminate or worsen the issue which then gives you information about where in the circuit you need to investigate.
- try different inputs. I can supply line-level inputs to CD, Tape 1, and Tape 2 and sometimes the sonic challenge is in only one input. Then you know to look at connections and switches on that input
- adjust the tone controls. Sometimes defeating tone controls (I don't recall offhand which controls are present on the D540, so forgive me if I err) -- by turning off loudness, or subsonic filters (infra-defeat), or simply twiddling the bass/treble knobs -- can eliminate or worsen the issue which then gives you information about where in the circuit you need to investigate.
Heya JS thanks for the tips. Pretty sure i have tried most things including spray cleaning the pots. Tried different RCA cables and in different inputs but the problem remains elusive due to my lack of electrical skill and test equipment. Im pretty happy with the outcome at this stage. If anything more fails i guess i will need to ship the unit to a repairer. Nearest repairer to me is about 4 hour return drive.
But loving this punchy Proton gear. Always looking on ebay for another amp.
Dogum
Livin' the dream, then woke up...
Back to OPs original question for a moment. I have two of my preamps torn apart right now, a Proton p1100 and a Yamaha c80. There is no comparison between the quality and workmanship of the two builds. The Yamaha has a solid board with robust solder traces, components are well laid out. My p1100 has a circuit board that is flimsy and solder traces look closer to my transistor radio I had in the seventies.
How do they compare soundwise? I don't know yet. Parts are here for both but no time yet to get back to my repairs. Consesus is Proton has done a good job putting together components so they sound great. I expect my Yamaha to be like my other Yamahas, clean, quiet, uncolored.
No matter how the internals compare, I am happy to own both preamps.
How do they compare soundwise? I don't know yet. Parts are here for both but no time yet to get back to my repairs. Consesus is Proton has done a good job putting together components so they sound great. I expect my Yamaha to be like my other Yamahas, clean, quiet, uncolored.
No matter how the internals compare, I am happy to own both preamps.
teal'c
Nuclear Cardiac Parent
Oxidation of the pigments seems to be the consensus. No one has run a chemical analysis that I'm aware of. I saw one of these on ebay and posted about it. There was a small discussion, but I couldn't find the thread when I looked. Maybe I can find it later.
https://audiokarma.org/forums/index.php?threads/what-happened-to-this-faceplate.859190/
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zycamaniac
New Member
I've seen that happen to Gustard DAC-X20 and other anodized black stuff... My guess is the dye they use can fade with UV or other stuff, I've seen that on sun exposed aluminum parts, or that Gustard DAC-X20 on my rack.
BTW, if you ever find a Proton that uses TO-3 power transistors, or anything with a suffix "PRO".... Take care of it. Also recap EVERYTHING, and replace all of the wires that you can.
Proton have a habit of using very low quality PVC insulated wires, and over time, the plastic somehow become porous and all of the copper strands in it will oxidize. Replace them with something better.
Also the electrolytic caps, especially the smaller ones (Snap-in ones are usually made by Nichicon and other reputable companies, so they are usually fine), I once did small cap replacement with my proton preamp (forgot the model number, but the one with XLR output), and holy that sounds so so so much better after a few hours of burn-in with the new caps.
I have personally visited the company that used to supply torodial transformers to Proton, and the owner of the company is also a very good engineer. If you see a torodial transformer in your proton, it usually indicates that Proton was not cutting a lot of corners with that machine, and some recapping and a bit of wire replacement would usually do some magic.
Thanks for that teal'c. It appears to have happened to others as well but not that common for AK viewers.