The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Just to update you That's the radio repaired.It was ZD1 was short circuit. Thank you so much for all your help!

Sorry havent had a chance to get the soldering iron out yet. Will keep you updated

Thanks for the reply.
If one of the diodes had gone open circuit would it give the symptoms i have?
If Q1, Q201, ZD1 or ZD2 fail would i still get +13v to the main board and no 0v?

Radio Make and Model: Midland 76-900 PCB Number: PTBM134A0X PLL Number: LC7137 Test gear available: DMM, AMM, Dummy load, Frequency Counter. Symptoms: No output from PSU What is working: Works fine on external power What has been tried: nothing yet Did it suddenly happen ?: not sure Anything else th...

Thanks, will give it a go when i next have the soldering iron out. the radio is just slightly off frequency so i would of thought the trimmer would of compensated for it. Thanks for the advice on VR13. Will turn it down. Everything is the way it was when a got the radio with the exception of the rel...

OK, I have Wired it up as per follows. L35 - centre pin on switch - top in on switch to middle leg of 4k7 VR - right leg of 4k7 VR soldered to can L15. When i try to adjust the frequency on ch1 I can only get it to go as high as 27.60049 instead of 27.60125 with VR turned anti-clockwise. When turned...

SUCCESS! I have Ch1 low to Ch40 uk. Adjusting the VCO did the trick Thank you so much for your help. Now for the 4k7 VR. It states connect to "wiper of course tune" Where should this be connected to? Also the radio is slightly off-frequency should i put it back on frequency before adjusing...

so i am aiming to bring the voltage down rather than up? As i am geiing 7.94v on Ch40uk

Thanks

The old eprom worked fine for a while. it was in the radio when i got it.
So when adjusting the VCO should i be screwing the core in or out or should i just wing it?
When adjusting it should i just monitor the volrtage at TP2 until it rises or is there a set voltage i should aim for?

I've just tested checked the voltages at TP2.
Ch23: 7.83v
Ch24: 7.89v
Ch25: 7.96v
Ch26: 7.92v
Ch27: 7.92v
Ch28: 7.91v
Ch29: 7.92v
Ch30: 7.92v
Ch35: 7.93v
Ch40: 7.94v

So i guess i need to adjust the vco?

I've got the wax out. should i be screwing the core in or out?

Hi,
I haven't had a chance to look at the radio again. I have been on decorating duties. Hoping to have a look at the voltages at TP2 over the next couple of days. Will keep you updated.
If i do have to adjust the VCO what is the best method to remove the wax from the core of the VCO?

Ok so i'll have to give that a try. What was is the best way to remove the wax from the VCO? Wil there be anything else needing adjusted after the VCO?

Thanks for everyones input. Much appreciated!

Richard

Sorry for the delay getting back to you. I have been on decorating duties. I think you misunderstood me. I was talking about the dot on the PLL. Pin 1 of the PLL being next to the recessed dot. I have the codes for you 25: O I I O I O I I I 26: O I I O I I O O O 27: O I I O I I O O I I = +8v I have ...

Can i just double check that you require the volateges for pins 9 - 17 ? pin 1 being next to the dot then working anti-clockwise

I am hoping to have time to have time to work on the radio over the next few days.
Would yo like these reading before returning the resistor array or after?

Thanks for everyones help on this

Also when you assembled the PCB, you did make sure that the resistor array had pin one (marked with a dot usually) at the same end as the voltage regulator ? so the resistor arrays pin 2 should line up with pin 1 of the EPROM. Double check as well that you installed all four jumpers correctly on th...

Just got the EPROM back from spectrum comunications ans he said it checks out fine. I'm at my wits end now, can't work out where i'm going wrong. I've lost track of how many time i have check my connections.

The old eprom was removed because it was going haywire. Transmitting away up on the 10M band The old eprom was removed a couple of months ago and the radio was working on all channels and on all bands and still does when the eprom is switched off (see 1st post). I checked it with a frequency counter...

Radio Make and Model: Superstar 360FM PCB Number: PB010AB PLL Number: MC145106 Test gear available: Dummy load, frequency counter, digital VOM, analogue VOM Symptoms: Ch 26 - 40UK missing What is working: High, Mid, Low band when eprom is turned off What has been tried: checked and double checked al...

Radio Make and Model: Rotel 240 PCB Number: PTBM134A0X PLL Number: LC7137 Test gear available: Digital VOM, Analogue VOM, Frequency Counter, Dummy Load Symptoms: Noisy TX What is working: Everything What has been tried: Switch cleaner mic gain VR. Checked connectionm Did it suddenly happen ?: Fault ...