Codar CR-66 Comms Receiver. Service info.

[gezza123]

HI:Guy's as you may well know, I have been looking for the manual for the CODAR CR-66 Communication receiver for some time to no avail.
So as promised to (Dave W).I have now got what I think may be a useful service manual that can be used to help service the CODAR.CR-66 ,and for anyone who maybe looking for information.
I have put this together in an easy format for us to trace and follow the circuit and layouts and help service in the future.
The circuit shown is a modified version of the original ,so you will have to study the manual to understand where the modifications are located ,look for the (M) if you have got an original model.
I am putting this on the site for everyone who may need it, and hope that no one will try to sell or profit from it .There are 17 pages so I have put it into 4 zip files.
PS:if anyone has got a CR-66 if possible could they please let me know as I am trying to find out how many were made and where are they now,and is there still some out there not assembled.

Please forgive me for any error's ,and the hand drawn circuits.Thank you Gezza

[dave walsh]

Looks pretty comprehensive to me Gezza-thanks a lot! I will be going north at the weekend [via the NVCF] will get those photos next week. Remind me again-just the underneath of the set? Are there serial No's on these? Obviously, I can't see from the S East. PM me your address so I can post prints to you from Rammy. Dave W

[murphyv310]

Brilliant Gezza!.
I have just got a CR66 from Kalee99 and the alignment is well out. Good set though, and one I wanted when I was a lad!
Thanks for the info!

[gezza123]

HI.DAVE Address sent.gezza

[murphyv310]

Hi.
There are a couple of small anomalies in the circuit! The Audio take off for a tape recorder ETC is drawn incorrectly the 10nf cap goes to the ECC81's second cathode not the grid.
Also the AVC resistor 470k goes to Diode 2 of the EBF89 not the cathode, some of the values don't tie up with this set, although that might just be modifications during the life of the design.

[murphyv310]

One other wee thing on the modified circuit on V8 the EF85 pin one is going to chassis it should be either disconnected or returned to pin one as both pins 1 & 3 are cathode.

Regarding the set I have here, at first glance it looked quite a reasonable construction job, unfortunately the work was quite poor and the performance was very bad, after a poke about about half a dozen soldered joints gave up, there was a noticeable lack of flux and the joints looked very dry, a lot of the resistors were way off value reflected in wildly wrong voltages. One worry is the capacitors used, these were Lemco types from the 60's but they were rated at only 125v clearly too low as some had 150-170v across them, this and leads not dressed or cut short. So far I have replaced most of the out of value resistors, fitted 400 v poly caps and tidied up connections and dressed bare leads.
Already the sensitivity is well up, the aerial coil on the low range was wrongly wired and that band now operates very well.
I don't like the AVC nor the IF gain circuitary as it tends to lead to distortion unless the gain is high up.
I will finish it tomorrow and post a picture of the underside.

[murphyv310]

Hi.
Here are a couple of pictures one of below and the other of the front.
One small mod to improve strong signal performance is to remove the 1 meg from the G1 of the ECH81 and connect a 220k from the G1 to pin 4 of the first IF transformer. this gives the ECH81 AVC thus reducing distortion on strong signals.

[Paul_RK]

Interesting to see that particular pattern of pointer knobs, obtained I suspect from Roberts! They were used for wavechange on the R77/R88, the company's last valve portables which probably had a rather shorter production run than had been hoped: then for years afterwards they were fitted in place of the usual wavechange knobs on various Wireless for the Blind Fund sets - models R200, R300 and R303 at least - to give tactile information as to the current setting of the switch. Might be worth knowing if somebody's stuck for finding the right knob for a CR66. The R77 and especially R88 are scarce sets commanding quite a premium, but the WFBF transistor models come up from time to time and one of those might not mind having its knob exchanged for the standard type.

Regards,
Paul

[gezza123]

HI.Trevor,Thank you for your feedback very much appreciated.
Wow yours look very clean inside and well laid out.
Checked mine again,and yes you are correct pin 1 marked on the circuit should be pin 6 on the EF85,as pin 1 is internally connected.well spotted.

The EBF89 D2 is pin 8 and is conected to the 470k AVC.

Now regarding the ECC81 pin 7 on mine is connected to the ETC output,
I have just done a scope test and found that it lets me put both input/output signals to and from the ETC.
This may have been done when someone wanted to use it as an amplifier as the solder joints are original.I did notice some distortion when useing the gain I.F.GAIN control, but now leave it full On since I did the B.F.O modification.And don't need to turn it down .Thanks again for the feedback anymore will be welcome.Gezza

[gezza123]

HI:Paul,yes the AE trimmer is original I still have the full set for mine but thought I would give it a bit of life.all these new knobs were used on my Induction hobs 15 years ago waste not want not.Gezza