TX-606 / TX-6700 Recap

xlbee

PIONEERFREQ
Subscriber
Just finished recapping and testing a TX-6700. Everything seems to work great so here's some pics and a recap list. This should come in handy as there are no parts lists in any of the online service manuals I could find.

Before:

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During (note masking tape to hold string so I don't have to figure out how to restring later):

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After:

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Apart from the caps in the list, markthefixer recommends changing q7 and q8 from 2sa725 to Mouser part number 512-KSA992FBU as a preventative measure.

Please also note that there are some caps in this unit that can affect the alignment, loop filter and ctr freq and separation. They are clearly indicated in my parts list. If you change any of them you may need to have your tuner professionally aligned if you don't have the equipment or knowledge to do it yourself. YOU HAVE BEEN WARNED!

Standard disclaimer: The attached parts list represents a snapshot in time. It's the right list for my unit, yours may be slightly different. Mouser part numbers change and they run out of stock so you may need to make some substitutions. The list should also be inspected by one of the AK gurus (you know who you are) to ensure it meets with their approval. The mods are more than welcome to publish it in the AK recap database if approved by one of the AK gurus.
 

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  • TX-6700 Recap List.pdf
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  • TX-6700 Board Before.jpg
    TX-6700 Board Before.jpg
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  • TX-6700 Board During.jpg
    TX-6700 Board During.jpg
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  • TX-6700 Board After.jpg
    TX-6700 Board After.jpg
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with the piicture of the original it looks like we are ok with regards to the UKL low leakage caps, just a few tantalums in there, no orange low leakage ones, the rest LOOK like light blue nichicons...

since we didn't have a parts list to distinguish ceanl cssa csza caps from the rest we have to go on appearance.

And I have been SO wrapped up lately that I didn't have time to think through the implications of things during the earlier thread where the "keep yer mitts offa dis" list was generated..

I'll almost BET that the caps that weren't changed due to alignment concerns were mostly tantalum caps..

I hope you have kept (at least for a while) all the old caps for reference, Believe it or not, I USUALLY do. some sets get dumped after a while when they are unremarkably different from a reference set kept for each model, but the "library is over a cubic foot if tightly packed.
 
3 of the 10 "do not touch" caps are tantalum. (The one other tantalum on the switch board I changed). You are correct, every original electrolytic is light blue Nichicon so I was fairly certain that none of them were low leakage.

There were two caps that were fairly close to one of the FM chips that "just in case", I wrote the cap number on with a Sharpie marker.

It's funny, I test every cap I pull out and every cap before I solder it in and in close to 100% of cases the old caps have a higher than rated capacitance value.

Anyway, all is well. It pulls in AM and FM stations at least as well as before I started.

Another one done.

An SA-7700 is next.
 
Mark, Would it be advisable to install low leakage UKL series caps in a tuner in place of the regular, (I assume) light blue original caps? Any disadvantage/advantage, besides temperature rating and cost vs using UPW's? I have a HH Scott R326 receiver that I'm going to recap, and all the caps on all the boards are the same series of light blue Rubycons. I'm thinking of using UKL's on the Tone, EQ, AM and FM Tuner boards, and UPW's on the Power Supply board, haven't ordered them yet, though. (More info and pics of it over on the Vintage forum)

xlbee, On my SX-780 and SX-1050, I swapped out all the electrolytic caps using the latest lists available, and had no noticeable effect to either tuner. I swapped each one one at a time, marking the old one so I could reinstall it if it went haywire. One cap on the SX-1050 slightly had an effect on the tuning indicator meter, bringing it slightly more centerline, compared to before, but the sound and stereo separation was the same. My SX-780 tunes exactly like it did before the recap, The SX-1050 was off on the tuner scale by .3 on average across the dial before and after the recap. AM on both work as well as before, except it sems quieter. Like you stated, It's not generally recommended to recap your tuner unless you plan on having it realigned, just posting my experience, but maybe you can try substituting the last few caps, saving the old ones for reinstallation, in case, to see if it throws things off or not.
 
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Chances are the circuits wouldn't be able to take advantage of the lower leakage of the UKL's but I don't see it hurting anything. The ONLY difference would be a slightly lower noise floor IF certain circuits meshed well with the different leakage specification.

The solid aluminum caps and tantalum caps had the lower leakage specs (at first in some cases, but not so any longer) but were primarily used for their smaller size and somewhat for the "prestige".
 
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