Hi all,
apologies if this topic has been discussed before but a quick search in the forum did not bring anything relevant.
A few days ago I acquired a beautiful and fully working Pioneer TX 9500 tuner. It has all original electrolytic caps, therefore I am planning to recap the power supply and audio frequency boards. Not too sure about the MPX and IF boards yet as I don't have the equipment for an alignment.
I have noticed that the audio board has tantalum capacitors in the signal path. Initially I thought about replacing them with Nichicon FG series. Unfortunately due to their values, film capacitors would not physically fit.
Given that tantalums are low leakage capacitors, it might be reasonable to replace them with low leakage Nichicon KL series, or just leave them alone. I know that in all vintage Pioneer amps they used to have tantalums everywhere in the signal path and usually they get replaced with electrolytics, but I am debating with myself on this. I am assuming that the Pioneer engineers used them there for a reason (stability, low leakage etc).
Please let me know your experiences all vintage restoration gurus out there.
apologies if this topic has been discussed before but a quick search in the forum did not bring anything relevant.
A few days ago I acquired a beautiful and fully working Pioneer TX 9500 tuner. It has all original electrolytic caps, therefore I am planning to recap the power supply and audio frequency boards. Not too sure about the MPX and IF boards yet as I don't have the equipment for an alignment.
I have noticed that the audio board has tantalum capacitors in the signal path. Initially I thought about replacing them with Nichicon FG series. Unfortunately due to their values, film capacitors would not physically fit.
Given that tantalums are low leakage capacitors, it might be reasonable to replace them with low leakage Nichicon KL series, or just leave them alone. I know that in all vintage Pioneer amps they used to have tantalums everywhere in the signal path and usually they get replaced with electrolytics, but I am debating with myself on this. I am assuming that the Pioneer engineers used them there for a reason (stability, low leakage etc).
Please let me know your experiences all vintage restoration gurus out there.
DONT touch the IF/MPX sections UNLESS you have specialised RF test equipment for aligning RF and IF --you have been warned !
Unless you know the Tantalums are faulty don't change them for standard electrolytic,s it isn't just low leakage they are good for --good stability -power dissipation-good HF characteristics -low esr etc .
Tantalum Capacitors Review | Engineers Edge | www.engineersedge.com
Unless you know the Tantalums are faulty don't change them for standard electrolytic,s it isn't just low leakage they are good for --good stability -power dissipation-good HF characteristics -low esr etc .
Tantalum Capacitors Review | Engineers Edge | www.engineersedge.com
Just replaced all the elctrolytic capacitors in the power supply and audio board with fresh Nichicon FG series.
I bet those black Nippon Chemicon would still be ok but I wouldn't leave something 40+ years old in the power supply.
Tantalum capacitors on the audio board are fine, so I left them in place.
I've also replaced the bridge rectifier diodes with new 1N4007 diodes. Voltages are spot on.
I am not planning to change any electrolytics on the IF and MPX boards as they are all Nippon Chemicon caps and I don't expect them to be stressed too much.
The only electrolytics I replaced on these boards are four of them across power connection and earth.
Check these two pale blue Sanyo capacitors that I removed from the rec calibration circuit. These are small 1uF/25V.
If you zoom in you will notice the bulge on the bottom.
These are notorious for failing and developing high esr values.
Unfortunately, there are three of them in the MPX board, which I bet will look the same and they are of small values. Would it be ok to replace them with Nichicon KL series or Wima MKS2 film capacitors?
So far the tuner works fine and tunes in. In fact, I am able to get FM stereo reception with 0.5 out of 5 on the signal meter using just a wire of 15 cm long as an antenna and the tuning meter is dead centre.
I bet those black Nippon Chemicon would still be ok but I wouldn't leave something 40+ years old in the power supply.
Tantalum capacitors on the audio board are fine, so I left them in place.
I've also replaced the bridge rectifier diodes with new 1N4007 diodes. Voltages are spot on.
I am not planning to change any electrolytics on the IF and MPX boards as they are all Nippon Chemicon caps and I don't expect them to be stressed too much.
The only electrolytics I replaced on these boards are four of them across power connection and earth.
Check these two pale blue Sanyo capacitors that I removed from the rec calibration circuit. These are small 1uF/25V.
If you zoom in you will notice the bulge on the bottom.
These are notorious for failing and developing high esr values.
Unfortunately, there are three of them in the MPX board, which I bet will look the same and they are of small values. Would it be ok to replace them with Nichicon KL series or Wima MKS2 film capacitors?
So far the tuner works fine and tunes in. In fact, I am able to get FM stereo reception with 0.5 out of 5 on the signal meter using just a wire of 15 cm long as an antenna and the tuning meter is dead centre.
Attachments
Last edited:
IF you decide to change the three capacitors on the MPX board do it VERY carefully taking great care not to interfere with any surrounding component even soldering use a lightweight iron so that heat is not spread to other components .
With what you say about that signal strength on FM you have a very good RF circuit design there that's stable , much better than many I have come across some would "die " for that sensitivity .
Yes go ahead and change them but be VERY-VERY-careful !
With what you say about that signal strength on FM you have a very good RF circuit design there that's stable , much better than many I have come across some would "die " for that sensitivity .
Yes go ahead and change them but be VERY-VERY-careful !
I've just replaced the nasty Sanyo capacitors, and those orange ELNAs in the MPX stage with Nichicon KL, low leakage caps.
Moreover, I replaced a blue capacitor across the signal meter which I thought it was another Sanyo, but to my surprise it was a Nichicon, which I replaced with a fresh Nichicon KL since I had it in stock.
Overall, I took good care to replace only the electrolytic capacitors which wold not affect the tuning performance, namely, power supply and audio circuit. I've only replaced a few capacitors in the MPX stage just because it was necessary.
I think stereo kicks in a bit faster now.
Tuner tunes in beautifully, stereo reception is excellent even with a piece of wire connected to the 75 Ohm terminal. If my signal meter is properly calibrated, this tuner is amazing...
Moreover, I replaced a blue capacitor across the signal meter which I thought it was another Sanyo, but to my surprise it was a Nichicon, which I replaced with a fresh Nichicon KL since I had it in stock.
Overall, I took good care to replace only the electrolytic capacitors which wold not affect the tuning performance, namely, power supply and audio circuit. I've only replaced a few capacitors in the MPX stage just because it was necessary.
I think stereo kicks in a bit faster now.
Tuner tunes in beautifully, stereo reception is excellent even with a piece of wire connected to the 75 Ohm terminal. If my signal meter is properly calibrated, this tuner is amazing...
Attachments
I am not selling it.. This is a keeper. No DAB, no RDS, no fancy digital display. This thing is built as a tank, made to last and it's servicable. Thick aluminium face plate, huge flywheel, the switches have a fantastic feel. Overall it is a pleasure to use it. Only thing that worries me is those pioneer custom ICs. Not sure if there are replacement ICS if something goes wrong with any of them..
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.