Hi all,
Well I’m off starting another restoration, this time the Sony TA-E88B preamp. I’ve noticed a few people have started threads or commented about this preamp, but they either petered out or didn’t get the info they needed. Hopefully I can create a useful thread that will help people in the future and I would really appreciate any feedback, comments and information you’re willing to share, to help me and others along the way!
This preamp is absolutely amazing and beautiful in its construction. It has a decent phono stage by all accounts and looking at the schematic it certainly seems to be the case.
Unfortunately, due to its age it’s almost definitely had a few different sets of hands digging around inside and I keep finding more and more little issues or things people have done, for reasons I am yet to find out. Luckily it was basically running when I bought it, so all the work I’m doing is to ensure its longevity, pretty it up and make sure that any bandaid fixes or mistakes are removed and repaired.
I have included a couple of photos below of about when I started working on it. I got part way into things before I started properly documenting, but you get the idea. I have some questions about alterations that were made, that are a bit beyond my level of knowledge, but I’ll post about that next so I don’t end up writing more than anyone wants to read in one post!
Lastly, if anyone has any documentation like the original user manual or any supplementary documentation other than the service manual, please share, it would be a great help.
Thanks in advance for any contributions.
Well I’m off starting another restoration, this time the Sony TA-E88B preamp. I’ve noticed a few people have started threads or commented about this preamp, but they either petered out or didn’t get the info they needed. Hopefully I can create a useful thread that will help people in the future and I would really appreciate any feedback, comments and information you’re willing to share, to help me and others along the way!
This preamp is absolutely amazing and beautiful in its construction. It has a decent phono stage by all accounts and looking at the schematic it certainly seems to be the case.
Unfortunately, due to its age it’s almost definitely had a few different sets of hands digging around inside and I keep finding more and more little issues or things people have done, for reasons I am yet to find out. Luckily it was basically running when I bought it, so all the work I’m doing is to ensure its longevity, pretty it up and make sure that any bandaid fixes or mistakes are removed and repaired.
I have included a couple of photos below of about when I started working on it. I got part way into things before I started properly documenting, but you get the idea. I have some questions about alterations that were made, that are a bit beyond my level of knowledge, but I’ll post about that next so I don’t end up writing more than anyone wants to read in one post!
Lastly, if anyone has any documentation like the original user manual or any supplementary documentation other than the service manual, please share, it would be a great help.
Thanks in advance for any contributions.
Audiokarma may be a better place for getting help on restorations of Sony gear from that era. If I don’t confuse Sony models, this was the preamp where the volume pot needs special care when disassembling and restoring, because you may otherwise lose ball bearings or the like, and if you do, turning the pot scrapes off something, rendering it beyond repair.
Interesting thread and I am looking forward to following it. I have one of those that I bought in Saudia Arabia when I lived there in 80's working for an oil company. It has a native 220 V power supply. I used it for a decade or so, then one of the phono channels went silent, and it got replaced by CJ PV-4 for a while and has been sitting quietly since. Seems like it sounded a bit hard compared to the PV-4 but it is a great looking piece, and I would be interested in restoring and improving it.
@DonG that sounds great, funny you’ve got the 220v version in the US and I’ve got the 100v version in AUS. I think it’s definitely worth restoring for sure. I have a Hegel v10 phono stage I’m using at the moment so I’m really interested in the comparison with that, but don’t have much else to compare with.
Just a quick update, I have so far replaced nearly all the easy/aged looking tantalum or ceramics with matched Wima film caps. I left any large value tantalum’s, the polystyrene and any others that I thought didn’t need changing or might alter the sound too much. I’ve also done some deep cleaning on all the PCB’s and removed any old flux, glue and conformal coating.
At the moment I’m in the process of stripping all the metal components and preparing them to be Cerakoted in the next couple of weeks. Unfortunately the top cover also needs re-coating, so I’ll need to work out how to get the text and other markings back on top, which will be the hardest part…
Some photos of the new film caps:
Just a quick update, I have so far replaced nearly all the easy/aged looking tantalum or ceramics with matched Wima film caps. I left any large value tantalum’s, the polystyrene and any others that I thought didn’t need changing or might alter the sound too much. I’ve also done some deep cleaning on all the PCB’s and removed any old flux, glue and conformal coating.
At the moment I’m in the process of stripping all the metal components and preparing them to be Cerakoted in the next couple of weeks. Unfortunately the top cover also needs re-coating, so I’ll need to work out how to get the text and other markings back on top, which will be the hardest part…
Some photos of the new film caps:
Some links for anyone wanting to follow up on doing this in future, I found these resources really useful.
Teardown and repairs on Japanese website Amp8:
http://amp8.com/tr-amp/sony/ta-e88.htm
The audio database has a good section on early Sony gear:
https://audio-database.com/SONY-ESPRIT/amp/ta-e88.html
The best free online version of the service manual I’ve been able to find so far:
https://www.dropbox.com/scl/fi/xxp2...ey=zo3m6x7pz2vvxxo8g2pt2fdrv&st=u63lfcbv&dl=0
Teardown and repairs on Japanese website Amp8:
http://amp8.com/tr-amp/sony/ta-e88.htm
The audio database has a good section on early Sony gear:
https://audio-database.com/SONY-ESPRIT/amp/ta-e88.html
The best free online version of the service manual I’ve been able to find so far:
https://www.dropbox.com/scl/fi/xxp2...ey=zo3m6x7pz2vvxxo8g2pt2fdrv&st=u63lfcbv&dl=0
One issue I’d love some help with, is a solder bridge that I located, which looks like it was added later and is not in place on any other online photos or referenced in the schematic. It was also done to both left and right channels, so was a deliberate alteration. Basically, someone has soldered over capacitor C409, bridging directly over the cap to one leg of C410, taking that cap out of the circuit essentially. I’m really not sure how this affects the output gain and would really appreciate if someone could help me understand why it would have been done and/or how the change affects the circuit.
I have removed the solder bridge for now so I didn’t forget, but it originally connected the two pins on the left (to the right of my finger) and the pin on the right, where I am holding the piece of solder to show the link. The two pins on the left are one side of C410 and C409. The pin on the right is the other leg of C409.
This is the part of the schematic showing where the connection was:
This is the artwork, with the black rectangle showing how it was soldered directly across the 68pf cap. Left and right channel numbering is incremented by fifty, so 409,410 on the left channel, is 459,460 on the right channel.:
I have removed the solder bridge for now so I didn’t forget, but it originally connected the two pins on the left (to the right of my finger) and the pin on the right, where I am holding the piece of solder to show the link. The two pins on the left are one side of C410 and C409. The pin on the right is the other leg of C409.
This is the part of the schematic showing where the connection was:
This is the artwork, with the black rectangle showing how it was soldered directly across the 68pf cap. Left and right channel numbering is incremented by fifty, so 409,410 on the left channel, is 459,460 on the right channel.:
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A first thought: C409 in conjunction with C410 (compenstion for the selected amount of amplification) and C406 in the local feedback path of the output buffer (Q411--414) creates an unintentional second pole for Q407-409 when RY301 is disengaged. It's a high impedence node there.
Frequency compensation is ok, but done twice is not, very much so when a relay or muting device is present.
The 88 is a marvalous pre-amp (I own a humble 86), but there are design errors, inevitable.
Frequency compensation is ok, but done twice is not, very much so when a relay or muting device is present.
The 88 is a marvalous pre-amp (I own a humble 86), but there are design errors, inevitable.
So basically there’s a chance it’s an intentional factory modification to fix an issue in the initial design and leaving it in place would be the ideal solution in this instance. Perhaps once I get it together again I will test with and without the bridge. I’m not knowledgeable enough yet to really understand how to properly test, but I’ll do some further research about the frequency compensation and see if I can understand it a bit better. Much appreciated!
Indeed. Production line experience can alter the final results yet undocumented in the ServMan.
A good oscilloscope will help, with enough bandwidth and set the probes on 10:1. With the input shorted (take the aux), you might see something at a high frequency... or not. HF is difficult to catch (search for 'Smith chart', and you'll understand).
If this unit needs the mod, beeter leave it as such.
A good oscilloscope will help, with enough bandwidth and set the probes on 10:1. With the input shorted (take the aux), you might see something at a high frequency... or not. HF is difficult to catch (search for 'Smith chart', and you'll understand).
If this unit needs the mod, beeter leave it as such.