my National RX-7200 88-108 MHz FM and 120VAC modifications/repairs

Superduper

Superduper

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May 30, 2009
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Hey. to you guys that are lucky enough to own an RX-7200, and wish to have your tuner FM band range adjusted to 88-108, I just want to say that Toshik has just recalibrated my tuner for me. I had a different solution in mind but this was far far easier. Just pop out the tuner and the FLD display, send it to him, and he will convert it for you. I found a few moments to install it today and it works properly. The only thing I forgot about is that stupid japanese AM section which tunes in 9khz increment steps instead of the 10khz steps that is everywhere else in the world. Not that this matters with an analog tuner but on a digital tuner, it does since you don't have an infinite range to choose from, only increment steps but this isn't Toshiks fault, that's just the way the tuner is/was designed.. However, the FM now works exactly like it is supposed to. Price for the update is, well that's between you and him. However, for me, my time is better spent nowadays on my other more pressing priorities right now, and I was happy to let someone else do the work for me. Heck, I don't even have time to open up and dust my machines much less do rebeltings... just no time. Just wanted to say that if you want it done, he can do it.
 
toshik

toshik

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Mar 1, 2015
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Thank you!
Just the metal shell is original - original transformer has only 2 leads in and 2 out and they are in a different colors.
Transformer is new, I like everything perfect even inside where nobody can see it.
 
Superduper

Superduper

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May 30, 2009
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toshik said:
Just the metal shell - original one has only 2 leads in and 2 out and they are in a different colors.
Transformer is new, I like everything perfect even inside where nobody can see it.
Click to expand...
Yes, I did see that it looks a bit different, in the windings section. But I just presumed that it was a variation on the components the manufacturer used. Looks a bit like a stanton?

On mine, I replaced it with Radio Shack 273-1511. It was 12.6v @3amps. Did the math and basically looks like perfect replacement. The mounting orientation of the shell bracket is different though so the only way to retain the original mounting would be to swap the shell like you did. With the radio shack shell, it would mount normal instead of diagonal which it seems would put less stress on the rear case as it would not hang as far out, and therefore, less leverage. But I am guessing the unorthodox mounting orientation may have to do with reducing noise since the windings on the orig transformer had unshielded windings. The good thing about the Radio Shack transformer is that it's fully shielded, even around the windings so that should not (and has not been) an issue. I decided that loosening the shell and maybe introducing a mechanical hum in the process, as well as losing the winding shields was not worth it to look perfect untouched. To me, having the shell say 100V when it's now a 120v transformer leads to confusion for future techs. Before swap was just tad under 23v. With RS transformer, now getting about 19.5V after the full wave rectifier with no load. That seems about in line with other 15V boxes on AC and no load (unregulated supply).
 
toshik

toshik

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Mar 1, 2015
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Nothing to worry - there are clear voltage markings on the new transformer coil. Original transformer is not shielded. Radioshack transformer is NLA, it's only 120 VAC and I'm sure it's the same OEM China brand I used.
 
Superduper

Superduper

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May 30, 2009
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Somewhere over the rainbow, USA
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toshik said:
Nothing to worry - there are clear voltage markings on the new transformer coil. Original transformer is not shielded. Radioshack transformer is NLA, it's only 120 VAC and I'm sure it's the same OEM China brand I used.
Click to expand...
yes, I wanted 120 VAC. Radioshack is of course going out of business but I found 3 at one store and snapped them all up since it's a common size used on boomboxes. You can still get them on eBay.
 
AE_Stereo

AE_Stereo

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Apr 24, 2012
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toshik said:
We have snake eyes in the club :-)
Fixed!
I also noted that the power transformer runs 24/7 even though they use a mechanical switch for power.
Click to expand...
You are a master electronic expert!

I have seen that many Akai "upside downers" have the AC power light "on" whenever it is plugged in. Even when the Power switch is off, indicating that AC power is on.
May be because they wanted to fix the power switch on the board, which is at DC level.
 
toshik

toshik

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Mar 1, 2015
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Up as reminder to all proud RX-7200 owners see what you are missing and there is no need to send the whole box over to me for the mod :-)
Based on my experience with the model I can also fix dead cassette channel (very common problem) etc.
 
toshik

toshik

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Mar 1, 2015
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I can also fix the all-static cassette channel problem.
You don't have to take those PCBs out if you don't want to - can send the whole radio if you'd like.
 
riker1068

riker1068

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Jun 5, 2014
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You work on other radios as well? I got a tech guy recently. He changes $40 for open inspect and deoxit. But I would rather offer a member the money for their work instead. I have a good 10 units that could use some work, and a few more extensive jobs as well. Cassettes are not my thing, so I will not be needing any rebelt work. Simple clean ups and pots lubes.
 
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