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I had a lot of fun cleaning up this old Sony STR-7045

Brett a

Brett a

~◦●○o0o○●◦~
I got this old Sony STR-7045 receiver (circa 1975 or-so) from a woman at work who was purging the crap out of her basement. It's been sitting in my barn since last autumn, earlier this week when I got the motivation to bring it in the house and have a closer look at it.

It was pretty dirty. But when I plugged it in, it seemed everything worked. Although the controls were quite scratchy sounding.



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Taking the cover off revealed that this thing is actually built quite solidly with huge caps and about 10# of transformer under the hood:

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It was also interesting to see that it has an internal switch to adjust the phono capacitance.

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Part 2:

So here it is all cleaned up:
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I removed all the knobs and soaked them in a strong solution of dish detergent before scrubbing them with a toothbrush. I removed the faceplate and cleaned it and the knobs up with Never Dull. I took a vacuum cleaner and soft paintbrush to the PCBs under the hood.

I also cleaned the veneer with denatured alcohol and re-oiled with furniture oil. The wood case is just a jacket over the outside of a metal cover---here it is sans veneer:

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I've never owned something with so many options for running in mono. (It also has a stereo reverse setting). This feature was fun to play with.

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So how does it sound?
PFG (pretty f*cking good)

For a rated 30 wpc, it seemed to drive my B&W 683s without breaking a sweat. And although it does not have the openness and resolution my main rig does, it delivered a pleasing amount of detail and good central imaging. The rear of the soundstage, however, could not really be called a soundstage; the rhythm section was back there somewhere behind the vocal and guitars, but exactly where was never really clear. I found myself adjusting the tone controls just about with each different recording. This was particularly interesting because I never feel a need to adjust the tone with my main rig (which doesn't have tone controls anyway). SO, what is it about this unit that makes it necessary to adjust the tone controls regualrly, where as I never need/want to with my other gear? (Same sources and speakers---everything.)

The phono section was very forgiving, less revealing than I am used to, but quite enjoyably so.

One thing I think I "got" from my two days with this in my system is how lower-resolving equipment like this can be a pleasure to listen to; it does not demand anything from you; it can just be played as background music without calling attention to its self.


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All-in-all, this was a really fun and enlightening experience. I'm not sure what I'm going to do with it now, It's not worth much money, I might as well put it back out in the barn in case I need it some day.

Anyway.
Thanks for looking.

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You sure that's a capacitance switch, and not FM de-emphasis? I'd have guessed the latter, given the microsecond unit of measure and location next to a tuner PCB.

Nice clean-up, did you detail the insides as well?

John
 
Beautiful! Nicely done --both the restoration and the write-up. It isn't just the TOTL gear that can be "worth" restoring. The lesser-powered models can still give great sound and a sense of nostalgia, etc..., and it is nice to see one restored/preserved.

The next step really should be a re-cap. Leaving the original capacitors, now well past their expected replacement dates and no doubt going off-spec, in there means you are not really hearing the full sound quality that the receiver is capable of. Plus, it's a "time bomb", as when one of the caps fails it may take out other, harder-to-replace components with it. Some old capacitors can literally "explode" and some of those release toxic and/or carcinogenic chemicals all over the inside of the gear when they do so. Best to get the aging things out of there and replace them with better-quality, longer-lived new ones, both for gear longevity and peace of mind.


Thanks a lot for sharing the write up and pics.
 
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Very nice work Brett - thanks for sharing all the pics. I have the earlier STR-6065 that I enjoy. But here in the middle of town, it has bad multipath FM problems. If mine also has the FM de-emphasis switch, would moving it to another position possibly help with the multipath?
 
I've never owned any TOTL. Maybe some creeping in that direction, but not at the top. But that is not to say that modest gear can't be fun - it most definitely can :)

Congrats on a nice clean up - very well done :)

30 WPC is pretty run of the mill, but Sony built solid gear and value. Perfect for a bedroom or a dorm room or a shop. Anywhere the music is going to have to "share" the space. Why not move it to that garage and build a modest system around it?
 
Thanks for the kind words everyone.

jdurbin1 said:
You sure that's a capacitance switch, and not FM de-emphasis?
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No, I'm not sure. It was an assumption.
Pray tell, what does an FM de-emphasis switch do?
Arkay said:
The next step really should be a re-cap.
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Having once recapped an old tube amp, I'm pretty sure I won't be recapping this rig --not my idea of a good time :no:
 
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Well an EE may jump in and explain the heck out of FM de-emphasis but FM broadcasters use a pre-emphasis time constant of 75 microseconds to the signal being broadcast as a way of reducing noise. De-emphasis restore the signal back the way it was. Leave it at 75.
 
I was thinking of the Dolby de-emphasis and that is why I was surprised that you had to open it up to switch it however on further investigation that was 25uS and probably came about long after this unit was built.

Apparently Europe and others used 50uS while US used 75uS thus the switch would likely be left in one position. Makes total sense now.

mike
 
Think of pre/de-emphasis in FM pretty much like the RIAA curve is for LPs: They're equalization curves.

That is, it was intended to minimize the amount of FM signal spectrum needed to broadcast the signal much like the RIAA curve for LPs allowed there to be more grooves on one side of a record.

Mashaffer is correct that Europe and America choose different equalization curves and, hence, different settings were required depending on where this Sony receiver was used. The fact that it is there tells me that our OP's Sony was an international model because Sony of America imported ones with out that feature to save on parts cost. I'll bet there's an AC voltage changeover block in the receiver, right?

I always liked that line of Sony receivers the STR-7045/55/65. Understated styling compared to the Marantz, Pioneer and Sansui of its day but all there sonically. They were extemely reliable, too, as my warranty station back then didn't see many come back for repair.

Very nice cleanup job, too!

Cheers,

David
 
Great job, and excellent description. I have a STR-6055 which is a virtual twin of what you have, just slightly more wattage at 35 per channel. It is a solid unit with excellent sound, very MAC like. Your baby is a keeper, try it with a pair Klipsch LaScallas if you can find them around. I 'd love to know what you think of the sound then.
 
Nice cleanup job.

Got both a 6120 and a 7055. The 6120 was bought by my uncle in Germany, while he was stationed over there. The 7055 is, as far as I know, a US model, but both have the switch. On the 7055, it's unmarked, though.

-J
 
If you stick it back out in the barn, at least kinda cover it up so you won't have to go thru cleanin' it again...And I'd keep it, put a cheap set of speaks w/it, use it as a "Background" system...
 
Sandy G said:
If you stick it back out in the barn, at least kinda cover it up so you won't have to go thru cleanin' it again...And I'd keep it, put a cheap set of speaks w/it, use it as a "Background" system...
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Done. And done. (and done?)

It's out in the barn lovingly providing tunes while I putter. I have a couple pair of Radio Shack monitors that I'm using. I might also consider hauling the Bose floor-standers down from the loft and trying those too.
 
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