Midland 7001 AM FM SSB No RF Output

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nimrod
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Midland 7001 AM FM SSB No RF Output

Post by nimrod »

Please could you help me.

I have just bought an absolutely mint Midland 120 Channel 7001 rig, it is unmarked and was in a custom made leather protective case, hence its condition.

It receives OK.
but when the mike is keyed the TX light comes on but there is not a sniff of RF out the back when tested into a dummy load via a decent REVEX power SWR meter. On opening the rig I fount the wipers had fallen of two 10K preset pots RV8 and RV9. I can replace them of course but I am not convinced that they will fix it. Any ideas please?
Cheers
Martin
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Snake Plissken
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Re: Midland 7001 AM FM SSB No RF Output

Post by Snake Plissken »

Hi Martin...

I'm not familiar with which mainboard would be in your radio....maybe a PTBM125A4X, or PTBM131A4X?

I have a Superstar 2000 lurking somewhere, that uses the 125 I think....

I think RV8 and RV9 are the trimmers to adjust the AM/FM and SSB signal meter levels IIRC...so I don't believe this could be causing your problem....

Do you have another proximity radio? If so, do you hear anything coming through on this when you try to TX on the Midland?

I would replace the trimmers anyhoo, and maybe check what voltages you have at the driver and final transistor...

Hope this helps....maybe someone else will chime in!

Cheers,
Dan
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Snake Plissken
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Re: Midland 7001 AM FM SSB No RF Output

Post by Snake Plissken »

edit....

I think it will be the PTBM121D4X board, same as a couple of Tristars and many others...?

I know there are more than one model of 7001...one with no FM and maybe others...
If so I think RV9 is for AGC adjustment...(automatic gain control).
Unidens (one or two)..
Cybernets (a few more)..
Stalker ST-9F DX Colonel FR360 Stag 357 Midland 79-900 Zodiac Tokyo Pegasus III Transceiver MkV
Cheiza CB702 workshop monitor :lol:
A few more, I forget...

Snake Plissken - Rescuing Presidents since a 1981 version of 1997 :D
speeddemon

Re: Midland 7001 AM FM SSB No RF Output

Post by speeddemon »

Hi martin Well If your gd with a solder iron i would first replace rv8 /rv9 or find some jump wires or use some 5k 1/4 watt resistors and jump center leg of rv8 to right leg of rv8 do same to rv9 then Try using a lighted dummy load google for one when you got a hold of one

key up the mike talk for a min see if lights up and how bright light is if you anit got one use a number 47 bulb out of a old flashlight center of bulb to center of ant connecter n piece of wire around outside of bulb/ground to outer ant connecter ground . before you send radio out to a shop for repair hope this helps you out . gd luck cheers n 73's
Last edited by speeddemon on 06 Sep 2017, 21:21, edited 6 times in total.
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ch25
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Re: Midland 7001 AM FM SSB No RF Output

Post by ch25 »

What is voltage on collector of final transistor on AM and SSB when TX?
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