BELCOM LS102 TUNING FAULT

[soundmanjim]

Hi Guys.

still didnt get my superstar 7000dx - got lost in the post - at least i got a refund!!

Anyway: i now have a belcom ls102, which is fine EXCEPT the flippin' thing will onl;y tune UP in frequency - even when i turn the tuning knob anticlockwise, it still tunes up.
whats gone wrong there? any ideas? It has been modded to cover 26-29Mhz.

any help would be greatly appreciated!

seeya

Jimbo 26CAT23

[Rick]

Have not seen one of there radios for over 20 years. I still have one some ware.

Common fault IC312 (MC14011B) Quad 2-input NAND Gate or it's one or two of the IC 306,307,308 and 309(MC14510B) BCD up/down counters. you can check to output of the MC14011B but you will need a Scope to see the pulses one side of the gate is + going and the other is - going, or dry joint on the VFO PCB. Hope this helps. Let know now you get on.

Rick.

[soundmanjim]

hi rick

thanks for the info.

having a look now; it seems intermittent 9sometimes it actually does tune down, then about 2 seconds later its only tuning up. im going for a dry joint here. I'll redo the joints and see what occurs.

also now noticed there is a dead carrier on usb. Feedback probably!

[soundmanjim]

latest. could be a dodgy 1khz/100khz step switch!!

[soundmanjim]

latest. note to self - check antenna is connected.

radio now seems to be in order!!

still desperate for some alignment tips if anyone knows which ones to peak for rx!!!

[Rick]

I will see if I can find the service manual. I know there some Coils you do not want to adjust or you will have a lot of trouble on your hands with out the right test gear.

Rick (Euro Radio Co).

[soundmanjim]

thanks rick. i have some test gear here; sig gen, dev meter, am mod, distortion analyser, scope, a few other bits; i used to work for the bbc doing their outside broadcast transmitters; but it's been a while since i poked a trimmer into a coil in anger!!!

thanks for your help.

[mike-g7bnf]

know the radio very well
there are two presets like ears very close to the phot interupter wheel
slightly adjust one of the presets that should cure the up/down error
if you wish the service man + my notes from the last 20yrs ill put them on yousentdit.com just ask

new email as from 2018

gm7bnf@yahoo.co.uk

...tnx - mike

mike

[Animal]

Mike,

I could use that info you have on the Belcom - my problem is similar to Soundmanjim's but mine corrects itself once the radio has warmed up.

Any info would be greatly appreciated.

[Rick]

Try adjusting two presets like ears very close to the phot interupter wheel, before you adjust them mark them so you can put them back ware was.

Rick.

[Animal]

Rick/Mike

Thanks for the suggestions - I'll have a crack at it at the weekend & let you know how I get on.