Pioneer RG-1 Refurb Project

[Timothy Flath]

Hi All
Just bought a Pioneer RG-1 and it is not functioning well at all. Power and lights come on good. Both meters bounce well and evenly when given signal (turntable via tape loop). Left channel no sound. Right channel very weak sound. Plan is to change out all 20 of the transistors as well as any out of spec Caps if I can find modern equivalents in hopes that it will rectify the issues. Have service manual so plan to do transistors first as I hear they are the more troublesome offenders.
Looking for a list of substitute transistors to change out the 22 listed transistors as per images attached. Wanted to know if anyone can tell me if the following mouser PN substitutes are OK?
2SC1312-F with 512-KSC1845FTA
2SC945-Q with 512-KSC2383YTA
2SC1384-R with 512-KSC2073TU or 522-ZTX694B
2SA684A-R with 512-KSA1013OTA
Thank You for any advice
Tim

 

[slimecity]

Hi Timothy.

I'd start with the 725's and 1312's. They are both known troublemakers.

Use the info here to guide you for common subs: http://audiokarma.org/forums/index....ilure-prone-whatever-and-replacements.731653/

 

[rcs16]

Plan is to change out all 20 of the transistors as well as any out of spec Caps if I can find modern equivalents in hopes that it will rectify the issues.

Willy Nilly changing of parts is not what I recommend as a good method to troubleshoot, it could be another comp,power supplies or a switch issue.
fyi: 2sc945, you should use ksc945c if needed, ksc2383 is only to be used in higher power applications such as power supplies and relay drivers.
2sc1384 is were you should be using ksc2883 and its complement ksa1013

The method to use, is to inject a sine wave into the inputs and trace the signals thru the unit, a sine wave source, scope and a AC voltmeter are the instruments to use in this case. Refer to the procedures on p18 of the SM.

You could start by measuring DC voltages and compare against the schematic.

 

[zebulon1]

A good Deoxit treatment would probably fix it.

 

[Timothy Flath]

A good Deoxit treatment would probably fix it.

First thing I tried - no improvement at all. Thank you though.
Tim

 

[Timothy Flath]

Hi Timothy.

I'd start with the 725's and 1312's. They are both known troublemakers.

Use the info here to guide you for common subs: http://audiokarma.org/forums/index....ilure-prone-whatever-and-replacements.731653/

Thank you muchly. The transistors was where I was thinking of starting so I got it partially right I guess. I will probably just order the lot (with the recommendations kindly provided herein) and merely start with replacing your recommendation Q's first where needed. Cost is insignificant and it always good to have the parts available immediately instead of waiting two weeks because I didn't get them all. I have this little toy that worked a charm on finding the bad transistors in an SA-8500II amp I tackled earlier this year:

Probably got very lucky there as per:

 

[Timothy Flath]

Willy Nilly changing of parts is not what I recommend as a good method to troubleshoot, it could be another comp,power supplies or a switch issue.
fyi: 2sc945, you should use ksc945c if needed, ksc2383 is only to be used in higher power applications such as power supplies and relay drivers.
2sc1384 is were you should be using ksc2883 and its complement ksa1013

The method to use, is to inject a sine wave into the inputs and trace the signals thru the unit, a sine wave source, scope and a AC voltmeter are the instruments to use in this case. Refer to the procedures on p18 of the SM.

You could start by measuring DC voltages and compare against the schematic.

I fully concur - didn't really think it was a willy nilly strategy. My thinking: First step was to try and ID any bad transistors best I can to see if they are the fault. I will undoubtedly have parts I don't use as spares for other Pioneer projects (working on a SA-8500 for $65 that needs help as well). Next I was going to do all the caps I can find suitable replacements anyway simply to ad longevity as I suspect many are far out of tolerance by now given their age. The RG-1 recap list on AK here already has a few on it that are obsolete. I have no sine wave source or scope yet - working on it as I really am a newbie to all this and just learning so will do that last. Thank you kindly for the suggested replacements and reasoning. Got some electricians at work that can help me muddle through the adjusting portion as they have signal generators and oscilloscopes etc galore. Sometimes a mickey of rum can go a long ways
Will do the DC voltage checks as well - great suggestions, thanks.
Tim

 

[Timothy Flath]

Here is an interesting one. First photo below is the Processor assembly board AWM-086 in my unit. Second photo is an image capture from the manual showing a Fuse in the top left corner with a large cap and other wires going into the board. Mine clearly does not have these items on the board yet it was a functioning unit as I bought it off the original owner who bought it overseas from a Canadian military PX (dual voltage model). Here is a refurb link I found showing this one is the same as mine: http://www.vintageaudioaddict.com/pioneer_rg1/pioneer_rg1.htm
Believe the difference is because it is a dual voltage model.
Hopefully there are no circuit differences as this would only affect the power supply side? No fuse as well in dual voltage models....

 

[slimecity]

There are quite a few threads on here about proactive replacement of 725's and 1312's.

The problem is that a transistor may test OK, but still be noisy or present other issues, which are only apparent in-circuit & under load.

If it were me - after deoxiting & cleaning all controls etc, I would shotgun & replace all those types of trannies first.

Another option is to try to use freeze spray to identify a problem transistor - this approach also works well.

As you can see, there are differing opinions on what to do in this case, you will need to think about the options& form your own views on the way forward.

 

[Timothy Flath]

There are quite a few threads on here about proactive replacement of 725's and 1312's.

The problem is that a transistor may test OK, but still be noisy or present other issues, which are only apparent in-circuit & under load.

If it were me - after deoxiting & cleaning all controls etc, I would shotgun & replace all those types of trannies first.

Another option is to try to use freeze spray to identify a problem transistor - this approach also works well.

As you can see, there are differing opinions on what to do in this case, you will need to think about the options& form your own views on the way forward.

Thank you slimecity - Having looked at the thread on problem Transistors I am completely sold on your notion that these should be swapped out as a matter of course. Have just placed my Mouser order for all trannies (realizing not all will be used if they are not problem ones) and Caps from this RG-1 list (Not sure why they only post caps on these threads as to me it make sense to change out all the problem child/noisy components including transistors etc as a matter of protocol.
http://www.audiokarma.org/forums/index.php?threads/pioneer-rg-1-recap-completed.424230/
The parts list was actually quite inexpensive and I will have left overs for other Pioneer Projects....

This AK sticky has been a handy site for all my Pioneer Gear but quite a few of the parts even on those lists are no longer obtainable - lots of homework doing these refurbs!!!!:
http://audiokarma.org/forums/index.php?threads/pioneer-recap-lists-sticky-suggestion.457663/

 

[Timothy Flath]

All
Here is the parts list I ordered. Hopefully I got most of it right?

 

[slimecity]

Hi Timothy - first things first - in terms of good practice, you want to fix a problem first before doing a recap.

The issues you describe could most likely be ascribed to being caused by noisy controls or problem transistors.

So while your list looks OK (Based on my quick look), you want to keep replacing transistors until the issue is gone. Once the unit is in a happy place, then you could proceed with recapping.

Good luck! Sounds like you have things in hand.

 

[Timothy Flath]

Hi Timothy - first things first - in terms of good practice, you want to fix a problem first before doing a recap.

The issues you describe could most likely be ascribed to being caused by noisy controls or problem transistors.

So while your list looks OK (Based on my quick look), you want to keep replacing transistors until the issue is gone. Once the unit is in a happy place, then you could proceed with recapping.

Good luck! Sounds like you have things in hand.

Many thanks Slimecity, my plan precisely - While I am waiting for the bits to arrive I am going to strip down the two main switches (Tape Monitor and Processor) like I did with my SA-9500II and the SA-8500II units. Will see if that does anything before moving onto transistors. Both amps got to the point where the switches were so horribly intermittent that any kind of dusting with contact cleaner was simply not working anymore (in particular the tape monitor switches and the tone defeat switches). That is the trouble with switches open to atmosphere me thinks. They were cutting in and out big time so I finally opened the units up, took out all the switches off the various daughter boards and took the cans apart and gave them a thorough scrub/cleaning as per post #6 in this link:
http://audiokarma.org/forums/index.php?threads/sa-9500ii-restoration.667561/

They both work flawlessly now with no hint of an issue going on many months now. After I did that I did a full recap on both. What a huge difference that was. I think they sound better than all the Quad refurb/upgrade kits I did on my Quad units: 2 X Quad 44, 1 X Quad 405-2 1 X Quad 303 and a Quad 34
I have a special place in my heart for the Pioneer stuff though as per (where this will hopefully someday find a place):

 

[rcs16]

So while your list looks OK (Based on my quick look), you want to keep replacing transistors until the issue is gone. Once the unit is in a happy place, then you could proceed with recapping.

I wish that this method works, lets see where it gets the op and if he needs further assistance if unsuccessful. I hate guessing at what is wrong, since it has proved me wrong so many times. I laugh that it is sometimes the 2 cent diode.

 

[Timothy Flath]

Part 1 of repair attempt

 

[Timothy Flath]

Part 2 of repair attempt:

 

[Timothy Flath]

Part 3 of Repair attempt:

 

[Timothy Flath]

Part 4 of Repair Attempt:

 

[slimecity]

I wish that this method works, lets see where it gets the op and if he needs further assistance if unsuccessful. I hate guessing at what is wrong, since it has proved me wrong so many times. I laugh that it is sometimes the 2 cent diode.

Recently had an issue in the flat amp board of my Sansui AU-X1. This amp is horrendously complex.

Replaced transistors, zeners - did a recap just in case. But there was still a really intermittent loud crackle in one channel from time to time.

Did an exploratory tug on one of the three wires from the power supply board (going to pass-throughs on the main board) and that set it off. It just goes to show that I should have done a simple reflow as a first step. That sorted it.

This can be a confusing area at times, for sure.

 

[Timothy Flath]

Part 5 of Repair attempt. Really thought this might actually do it because of the horrendous shape the contacts were in on the two switches I cleaned. They were literally blacked with age and oxidation but look brand new on the inside now. Not surprised there is still an issue though so moving forward to the next phase of the plan which is troubleshoot the Transistors on the Left channel since the right channel appears to be working good at this point. More to follow when I receive all the bits in the mail.