Hacker RP 25 -Motorboating now now AM and high quiescent current

[Bonky]

Hi all, many thanks for all the advice and encouragement..but I'm going to ask 'Murphy' (aka Trevor) to repair it for me..to the relief I'm sure of most of you (and me)!

Murphy...I've sent you a PM

Best wishes,

Richard

[Murphyv310]

Thank you Richard.
I've replied to your PM.
I intend to keep the thread alive once I have the radio.

[Bonky]

Thank you Richard.
I've replied to your PM.
I intend to keep the thread alive once I have the radio.

Thanks!

I've sent you another (cheeky) request...

I only share some of the blame for the state of the electronics...(!)

Have just received a book "Electronics for Dummies" (an apt title I think)...

Best wishes,

Richard.

[Murphyv310]

Hi Richard.
No problem at all.
Remember we all started from scratch ourselves. The thing though being a 1954 model when I was old enough I got help from my Dad who had built many Radio's and I think three or four Televisions. Not only that there were plenty of TV repair shops, they were only too glad to give the young lads old scrap TV's and Radios (helped them to shift the scrap) and answer the occasional question too.
It's much harder for the novice now, you don't have many repair shops on street corners, in fact you'd be hard pressed to find such an establishment and even more find an engineer that fixes stuff older than 30 years.
It must be hard for people now with that sort of interest. The net is good but hands on and one to one advice doesn't really come over a PC screen.

[Bonky]

Hi.
Personally I'd not recommend either the signal generator you have nor the one you are looking at for a beginner, they are too complex to drive and neither has an internal audio test tone modulated onto the RF output.
I'd be looking for an older simpler one like an Advance, simple controls and accurate enough for a tranny radio and cheaper too. To be fair you've already paid out a good few quid and if you think this is going over your head stop and perhaps work on something easier or make a few little projects to get familiar with electronics.
If you wish to carry on I'm sure we will help as much as possible.

Hi,

There are 3 models on eBay at present. Are these the ones you mean?

(I know one or two  may not work(!)).

https://www.ebay.co.uk/itm/122770424421?ul_noapp=true

https://www.ebay.co.uk/itm/322802544753?...0352.m3747&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20160928094120%26meid%3D8a7eb24789fa442186250cb0fd44c0c8%26pid%3D100352%26rk%3D3%26rkt%3D12%26sd%3D122770424421&ul_noapp=true

https://www.ebay.co.uk/itm/Advance-Engla...2802544753&_trksid=p2047675.c100005.m1851

Any advice gratefully received...


BW

Richard.

[pwdrive]

The Advance 62 RF generator...........the other two are AF generators and will be of limited use for your radio career.

Lawrence.

[Murphyv310]

Hi.
The first one would be the of choice for me. It has modulation and is a good all rounder. The other two are not ones I'm familiar with but no doubt fine too.

[Murphyv310]

Hi.
The radio was delivered today.
I have dismantled the set and set up the scope etc. First quick check was on the local oscillator and lo and behold there was nothing. this turned out to be a crack on the print onto the base of the AF178 replacement, repairing this has restored the oscillator. I have replaced the AF178 with a known good AF117 on the component side of the PCB.
The If amp board has at least two problems, the substituted AF114 has tin whiskers so I'll replace that first, only snag is the last IF transformer has been opened up and it doesn't look too happy.
Will report back later as i'm not around tomorrow or Thursday.

[Murphyv310]

Hi.
Well I may have been lucky with the last IF transformer, only time will tell. The problem with these is you mustn't just try and remove the screening can, you need to remove the full can unsolder the pins and the lugs for the can and then remove. Also the ferrite round the can is held in place with masking tape and glued so damage can be done. In the past I have heated the the can up so the glue softens then you can gain access to the diode. Incidentally the Diode is OK.
The lesson to be learned is not to dive in, ask and take heed of the advice. Anyway fingers crossed that the repair to the can works, other wise we need another can from a scrapper which unfortunately I don't have.

[Murphyv310]

Hi.
Well the can has had it's chips, although the connection has been made OK the ferrite around the coil is in a sorry state, it was crumbling before my eyes so I didn't hold a lot of hope TBH.
I have good signal to the last IF amp but the level on the collector is far too low and it wont peak up. I do have another IF transformer from an unknown board but it uses an external detector diode so I'll cobble it in on Friday and see if we get the set up and running.
Oh incidentally the motorboating is intermittent, It's caused by the plug to the audio board, possibly a poor soldered connection on the earth wire pushing them or twisting clears the fault.