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 Post subject: Seeking schematic for Crown TR-690
PostPosted: May Sat 16, 2020 3:00 am 
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Joined: May Sat 09, 2020 10:21 pm
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Location: Detroi, MI
I searched before whipping up this post, but the search isn't working very well for me.

My Crown TR-690 likely needs a recap. I dont want to start fiddling with it unless and until I have a schematic. Thus far, my search has been fruitless. Sans doesn't appear to have covered that model, and The Schematic Man also had nothing. I'm hopeful that Crown chassis were used across multiple models. Does anyone have the schematic, or at least suggestions of other places I could look for it?


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sat 16, 2020 4:47 am 
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I could not find anything for the TR-690.

However there is a schematic on the Radiomuseum site for the TR-680
which has a very similar chassis parts layout. Pics are there for both radios.
They are both six transistor sets, they use different transistors.

You be the judge if it's worth looking into.


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sat 16, 2020 6:35 am 
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Location: Detroi, MI
I'll do a little more looking into that tomorrow. Thanks!

I'm looking primarily for information on the electrolytic caps. With help of a flashlight, I found markings on three of them. They are, as best as I can tell: 50-microfarad/10-volt, 50-microfarad/3-volt, and 5-microfarad/6-volt. There is a fourth, but with resistors and disk caps crammed all around it, I'd need to consult a schematic or desolder it to determine its voltage and capacitance.


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sat 16, 2020 7:05 am 
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Hi Dan. From what you described the 4th electrolytic will most likely be for the a.g.c. Probably a 10uf,but that's just a guess. A 15uf is a possibility too.


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sat 16, 2020 7:11 am 
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Dan, I'll letcha in on a dirty little secret regarding battery Transistor radios; except for the Electrolytic connecting to the volume control wiper, which is normally a low value, 10 uF or under, the others don't matter. And again, that doesn't have to be exact, just ballpark.
In your case, sounds like the 5 uF.

You can use a 10 uF for a 50 and vice versa, and the performance will be good either way. AFA voltage ratings, modern starts at 16 volts, which is more than ample for a 6 or 9 volt battery circuit.

_________________
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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sat 16, 2020 5:45 pm 
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Joined: May Sat 09, 2020 10:21 pm
Posts: 129
Location: Detroi, MI
I've been looking for capacitors with the ratings indicated on those presently installed, with little luck. Perhaps I would be better off ordering an assortment? I do have time to figure it out, and I'm loathe to use the Crown as a first soldering project. That latter is a topic for a new thread...


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sat 16, 2020 5:59 pm 
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Location: Mountains of Mourne. Ireland.
Modern day electrolytic capacitors have become so much smaller since the 1960s - 1970s
Some of the old μF (microfard) values are no longer common... so choose the next nearest capacitance value, up or down.

... I buy the 35V and 50V ones today to replace the old 3V, 6V + 10V ones and 85°C is good enough for transistor radios.
It's foolish to hunt down 3V 6V or 7V caps :shock:
viewtopic.php?p=2864980#p2864980


:) Greg.
oh... the Voltage rating of an Electrolytic Capacitor is how much juice that it can handle - this can be increased.

Edit: 4.7μF (microfarad) and 47μF are today's common values.
use these to replace your 5μF and 50μF

------------

A selection of Today's common μF (microfarad) values can be seen here..
UK store - - do not purchase, shopping example only.
viewtopic.php?p=3031496#p3031496

------------


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sat 16, 2020 6:59 pm 
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Location: Panama City, FL 32401
egg wrote:
Modern day electrolytic capacitors have become so much smaller since the 1960s - 1970s
Some of the old μF (microfard) values are no longer common... so choose the next nearest capacitance value, up or down.

... I buy the 35V and 50V ones today to replace the old 3V, 6V + 10V ones and 85°C is good enough for transistor radios.
It's foolish to hunt down 3V 6V or 7V caps :shock:
viewtopic.php?p=2864980#p2864980


:) Greg.
oh... the Voltage rating of an Electrolytic Capacitor is how much juice that it can handle - this can be increased.

Edit: 4.7μF (microfarad) and 47μF are today's common values.
use these to replace your 5μF and 50μF

------------

A selection of Today's common μF (microfarad) values can be seen here..
UK store - - do not purchase, shopping example only.
viewtopic.php?p=3031496#p3031496

------------


Or replace this 8uf with a 10!


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sat 16, 2020 7:33 pm 
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Joined: May Sat 09, 2020 10:21 pm
Posts: 129
Location: Detroi, MI
Using a 50-volt capacitor where once stood a 10-volt seems roughly analogous to using premium fuel in an engine designed to burn regular...or not nearly as bad as replacing a 10-amp fuse with a 30-amp. If I'm correct (my knowledge of electrical theory is a bit rusty), then I'd be more concerned with finding capacitors that are dimensionally as close to the existing units as possible.


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sat 16, 2020 7:49 pm 
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Joined: Jan Tue 31, 2012 1:55 am
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Location: Mountains of Mourne. Ireland.
Today's capacitors are about a third in physical size to the ones from the 1960s and '70s
use ones rated at 16V or 25V or 35V or 50V - - it's of no consequence.

I have explained stuff, and given you good advice.
It's entirely up to you what you do with that advice. lol


Greg.


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sat 16, 2020 10:49 pm 
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Joined: May Sat 09, 2020 10:21 pm
Posts: 129
Location: Detroi, MI
I will heed that advice when it comes time for the recap. Thanks!


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sun 17, 2020 1:16 am 
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Dan's Radio Room wrote:
I'd be more concerned with finding capacitors that are dimensionally as close to the existing units as possible.



https://www.allelectronics.com/category ... ors/1.html

The postage'll be more than the caps.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins/////////////////////////


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Sun 17, 2020 4:49 am 
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Joined: May Sat 09, 2020 10:21 pm
Posts: 129
Location: Detroi, MI
Yes, the parts would cost all of six bits. Of course, I'd also need solder, flux, and a solder sucker...


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Mon 18, 2020 2:05 am 
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Joined: Jun Tue 21, 2011 8:27 pm
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Location: Flint Hill, Virginia
Dan,

PM me with your address and I'll put a dozen or so popular value caps in the mail. No charge unless you want to cover shipping.

BTW, I sell replacement caps used in transistor radios for roughly 10 cents each. All are 50V and close to the same physical size to what the old ones were.

Mitch


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Mon 18, 2020 2:10 am 
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Joined: May Sat 09, 2020 10:21 pm
Posts: 129
Location: Detroi, MI
Thank you, Mitch. PM sent!


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 Post subject: Re: Seeking schematic for Crown TR-690
PostPosted: May Mon 18, 2020 2:23 am 
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Already packed up in a nifty padded envelope to be mailed first class on Monday.

Mitch


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