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Question about Technics ST-S4 tuner preset circuitry.

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Posted on November 4, 2020 at 11:03:32
Quadzilla
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Posts: 4163
Location: Southwestern Ontario
Joined: July 31, 2003



I have always liked the early-80s slim-line Technics components, and I found a very nice ST-S4 tuner this morning at the Goodwill. The price was right, and it works and sounds great. I downloaded the ST-S4 technical manual from hifiengine, but it is a bit different than my tuner.

The manual shows a battery holder with three 1.5 volt batteries to hold the preset memory. Mine doesn't have that; but it does have three 1.8v / 3.3F black and gold 'Gold Cap' capacitors at C914, C915 and C916 on the main circuit board that aren't shown in the manual, and two of them are bulging and leaking (centre/front in the photo).

Am I on the right track? They don't look difficult to replace if I can find the right ones, but I am used to capacitors that are rated in uF. These are 3.3F, and I haven't seen that before. Granted, I am no technician, so for all I know they might be quite common.







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RE: Question about Technics ST-S4 tuner preset circuitry., posted on November 4, 2020 at 18:16:38
Steve O
Audiophile

Posts: 12378
Location: SE MI
Joined: September 6, 2001
 Replacing those caps would be a wise move esp if physically leaking. Typical symptom of bad caps here is memory loss on power outage. While caps such as these wouldn't be found at your corner Radio Shack if they were still around, they're reasonably available at your favorite electronic supply house like digikey or mouser. Look for "super capacitor" or "double layer capacitor". IME, exact value isn't critical although voltage rating is. Physical size will also be a determining factor.

 

RE: Question about Technics ST-S4 tuner preset circuitry., posted on November 5, 2020 at 07:23:00
Quadzilla
Audiophile

Posts: 4163
Location: Southwestern Ontario
Joined: July 31, 2003
 Thanks for the reply. I am having a tough time finding 1.8 volt caps though. There are plenty of 3.3F ones, but the lowest voltage I can find are 2.7v; even at Digikey and Mouser. Nothing on eBay in China either.




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RE: Question about Technics ST-S4 tuner preset circuitry., posted on November 5, 2020 at 07:53:49
Steve O
Audiophile

Posts: 12378
Location: SE MI
Joined: September 6, 2001
 You can use the higher voltage version wo issue. Don't go lower. Here's where physical size becomes a factor. All else equal, higher voltage will be larger but there have been advances since the 80s so it's certainly possible to find caps with higher capacitance and/or higher voltage that will fit just fine. I replaced the "memory cap" in an 80s era RS receiver with one that was twice the stock capacitance and 2.7V where original was something like 2.2V. New cap was approx same size as old. Do try and duplicate lead spacing for ease of insertion and neat appearance.

 

RE: Question about Technics ST-S4 tuner preset circuitry., posted on November 5, 2020 at 07:56:47
Quadzilla
Audiophile

Posts: 4163
Location: Southwestern Ontario
Joined: July 31, 2003
 That really helps, thanks. The originals are 1/2 inch Dia. X 1 inch High. The are tightly spaced, and the cabinet sleeve won't allow any taller. I should be able to find three 2.7V / 3.3F caps, I hope. Cheers!




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RE: Question about Technics ST-S4 tuner preset circuitry., posted on November 5, 2020 at 08:39:20
Steve O
Audiophile

Posts: 12378
Location: SE MI
Joined: September 6, 2001
 The supply houses almost always provide links to detailed data sheets so you can measure your parts and select new ones that match dimensionally. IME, the exact value of capacitance is not critical so you can increase or decrease within reason wo creating problems as space dictates. The primary effect of lower value will be reduced length of memory which may be of no or minor consequence depending on your expectations and how long you leave unit unplugged.

 

RE: Question about Technics ST-S4 tuner preset circuitry., posted on November 5, 2020 at 12:59:56
Quadzilla
Audiophile

Posts: 4163
Location: Southwestern Ontario
Joined: July 31, 2003
 I didn't spend a lot for the tuner, less than the equivalent of US$10, so I just wanted to practice recapping and other basic work. This is the closest (in voltage and capacitance) that I have found on eBay, and very inexpensive too. Would they be OK?






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RE: Question about Technics ST-S4 tuner preset circuitry., posted on November 5, 2020 at 13:41:52
Steve O
Audiophile

Posts: 12378
Location: SE MI
Joined: September 6, 2001
 It could be OK. OTOH, I'm unfamiliar with the brand and am wary of Chinese stuff from outside normal distribution channels. Remember the "sick cap" incident a while back? Personally, I'd look for something from the usual sources. As always, YMMV.

 

RE: Question about Technics ST-S4 tuner preset circuitry., posted on November 5, 2020 at 13:55:34
Quadzilla
Audiophile

Posts: 4163
Location: Southwestern Ontario
Joined: July 31, 2003
 I know what you are saying about Chinese stuff, and I don't disagree. This is a pedestrian tuner that cost me very little money, so I am not risking a lot if I waste another five bucks on the caps. The problem with the usual suppliers is that the shipping cost for three caps would prohibitive. I have a local parts supplier checking into it, and I am hoping that he could add them to his next order.




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Agreed, posted on November 5, 2020 at 14:16:18
1973shovel
Audiophile

Posts: 10117
Location: Greenville SC
Joined: February 25, 2007
 Mouser has Panasonic 3.3F @ 2.5V, measuring 20 mm L x 8 mm diameter (link below) which are shorter and narrower than the original memory caps in the tuner, so there should be no problem fitting them in.

Why gamble with Chinese caps of unknown quality?

 

RE: Question about Technics ST-S4 tuner preset circuitry., posted on November 9, 2020 at 14:05:33
Quadzilla
Audiophile

Posts: 4163
Location: Southwestern Ontario
Joined: July 31, 2003
 Well, the guy at the local parts supplier found a single 2.7V / 10F from Illinois Capacitor that he says will replace the three originals. The physical size is the same as one of the originals, so there won't be any fitting issues. Thanks for your advice.




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Good deal. (nt), posted on November 9, 2020 at 16:58:12
Steve O
Audiophile

Posts: 12378
Location: SE MI
Joined: September 6, 2001

 

All fixed, and ..., posted on November 19, 2020 at 12:34:04
Quadzilla
Audiophile

Posts: 4163
Location: Southwestern Ontario
Joined: July 31, 2003



I decided against anything Chinese. Thanks again for your help.




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