Author Topic: 1964 Astrosonic - before I shotgun the caps....  (Read 2135 times)

Motorola Minion

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1964 Astrosonic - before I shotgun the caps....
« on: October 21, 2015, 01:48:21 PM »
I have a R20409 dated April 1964. Even with a good rooftop antenna, FM has "static" that sounds like a microphone on a windy day.
It is only slightly better in mono, even on the strong stations. AM sound seems better by far. After a cleaning selectors and pots, its pretty much equally crappy on both channels. :(

The amp and drivers seem Ok and all the "Nichicon" electrolytic caps have acceptable ESR. From what I read here, that may not be enough.

The reception, especially FM selectivity is poor. I would really hate to put efforts into a wholesale re-cap with it ending up worse than it is.
It is radio-hell in the mid-'lantic with a crowded dial, so this is important. 
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Dave

Consoleman

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Re: 1964 Astrosonic - before I shotgun the caps....
« Reply #1 on: October 21, 2015, 05:55:33 PM »
I have a 1970 Astro and the Nichion caps in that were done for, most measuring way high. A full recap helped FM reception in that one, so I wouldn't worry.

Mark

Motorola Minion

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Re: 1964 Astrosonic - before I shotgun the caps....
« Reply #2 on: October 21, 2015, 06:43:05 PM »
Thanks I guess I'll start in the FM section since the AM sounds pretty good.
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Dave

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Re: 1964 Astrosonic - before I shotgun the caps....
« Reply #3 on: October 21, 2015, 06:55:36 PM »
Caps is caps... they were not designed and built to work correctly for 50+ years, change em all and check all the resistors.
-- Aloha, Ken

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bluetantra

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Re: 1964 Astrosonic - before I shotgun the caps....
« Reply #4 on: October 22, 2015, 09:35:48 AM »
This is an -excellent- article on the aging of capacitors and their end-of-life:

http://www.emersonnetworkpower.com/documentation/en-us/brands/liebert/documents/white%20papers/sl-24630.pdf

Years ago in school, we were taught that electrolytics have an average life of about 10 years.  Many manufacturers today provide a life expectancy figure with their electrolytic capacitors, ranging from 1,000 or 2,000 hours to 5,000 and even 10,000 hours.  I just ordered a bunch of 5,000 hour Panasonic caps for an Astrosonic 500 that I'm working on.
Music:  the other non-addictive, mood altering non-substance.  Ask your doctor if Music is right for you! Common side effects include but are not limited to uncontrolled head-bobbing, toe-tapping, finger snapping, selective hearing impairment, and persistent melody flashbacks.

Motorola Minion

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Re: 1964 Astrosonic - before I shotgun the caps....
« Reply #5 on: December 15, 2015, 12:05:34 PM »
The R204 is next for a recap but after I finished recapping the 15 watt R211, It starts to "motorboat" at low or no volume. I reviewed the values and tried replacements in some key spots, but it starts this low popping after its on for a few minutes.

Time to start freezing transistors since it appears thermal-related.

First, Ill try disconnecting driver transformers to isolate the trouble between driver transistors and outputs. 
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Dave

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Re: 1964 Astrosonic - before I shotgun the caps....
« Reply #6 on: December 23, 2015, 11:01:19 AM »
The popping issue is thermal. I have chilled the driver and preamp transistors Q10-11 and Q14-15 and it stops. ECG102 and 102 A on order let's see.
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Dave

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Re: 1964 Astrosonic - before I shotgun the caps....
« Reply #7 on: December 29, 2015, 02:39:14 PM »
Well I thought I could order the PNP-Ge transistors but the usual places have only the silicon transistors :-[. I have found only one that really reacts when I heat it externally, so Ill see if I can find a replacement Germanium in a mid-60s parts set.
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Dave

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Re: 1964 Astrosonic - before I shotgun the caps....
« Reply #8 on: January 22, 2016, 10:11:13 AM »
Well, the 100% re-capped R211 chassis been playing awesome music from the University of Pa station 24/7 through some bookshelf Visonik 80s without issue for the last 5 weeks :o and I have another R211 waiting plus an R204 and another Astrosonic 100 needing caps. Im sure THOSE two will sound much better when Im done ;D
Sure its cold in my shop and the set is NOT in the cabinet, why would I see a heat issue under these conditions?

I cannot make it act up unless I heat any of the four driver transistors so I'm thinking that rather than replace them, I will add heat sink hats on those little cans and put it in the cabinet. I'm a cheapskate at heart so here goes nothing.

Its cheaper for sure since germanium transistors (NTE 102A) are not exactly a stock item at Allied, Mouser, Digi-key, etc. I would have to order them at a local NTE dealer.
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Dave

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Re: 1964 Astrosonic - before I shotgun the caps....
« Reply #9 on: January 22, 2016, 04:55:10 PM »
That sounds like a good plan Dave. You have nothing to lose by trying and it might just be all that is needed to make the unit reliable.
-- Aloha, Ken

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