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-   -   RA17 Rebuild and mod state query (https://www.vintage-radio.net/forum/showthread.php?t=163876)

coil1234 14th Feb 2020 4:44 pm

RA17 Rebuild and mod state query
 
2 Attachment(s)
Hello,
I have just started a rebuild of my early (Ser No N184) RA17. I'm initially looking at the 3rd IF strip and have found a few discrepancies between the circuit / parts list and the components actually fitted.
In this case R93 and R94 (1st IF Amp screen grid feed), which according to the circuit are two 47K in parallel, however on my unit I've found a 33k and 27k in parallel, additionally some resistors appear to uprated.

I'm wondering if this is a modification, my unit is up to mod state 37 and also has a red (letters) mod label on the rear, additionally it has a label on the rear which I believe means it was overhauled by Racal.

To this end does any one have a list of what each mod entailed?

Regards
Mike A

Racalrob 15th Feb 2020 11:26 am

Re: RA17 Rebuild and mod state query
 
Mike.

The receiver you own was previously used by GCHQ as indicated by the red modification label. Mod A is replacement of R84 from 1Meg to 22K ohms. Mod C was putting finger guards on the front panel behind the tuning knobs. Mod L was implemented so as the 1st and 2nd VFO ouptuts could drive an Astro FR-1002A digital frequency counter. The mod in question regarding the 2 x 47K resistors being replaced by a 33K and 27K in parallel was done to increase the screen voltage on V14.

Regards

Rob.

coil1234 16th Feb 2020 12:31 pm

Re: RA17 Rebuild and mod state query
 
Hello Rob,

thanks for the information. Yes, I can confirm my RA17 is ex GCHQ, it belonged to the father of the chap I brought it off who worked there. Also confirmed with some documentation.

I've just checked R84 in the calibrator and it has been changed to 22k, so that fits.

It looks as if the original paper capacitors have all been replaced in the past, however I'm replacing them all again along with the resistors for long term reliability.

That's why I was hoping to get a definitive list of all the components I want to replace, so I could order them in one go.


Regards
Mike A


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