FT 767GX power supply 13.5v regulation problem

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FT 767GX power supply 13.5v regulation problem

Postby vk5ht » Sat Dec 08, 2018 4:26 am

Boat Anchor Nut!
I have a FT 767GX that had multiple faults some factory faults but now works. One fault left is the 13v power supply suffers from poor regulation. Varies between 10v and 16v. The 24v side is good and is fixed. This 13.5v rail feeds the other modules VHF/UHF also so when the voltage drops so does the power out on these modules. This voltage drop is with modules installed or removed. At switch on it is at 12v on PS board and slowly climbs to 15-16 on RX which is what is coming from the transformer. Something is leaking. When keyed it drops to 10v on full power or on voice peaks. Replaced the 10amp bridge. An ESR meter shows my PS E.caps as ok and all other e.caps replaced on PS. There is only a small ripple to the circuit. VR04, R24,R25 and Q10 were replaced but I cannot adjust the voltage. Q10 is 10v-10v-10v on the leads. Q8 replaced. Q6,7,9 have not been replaced yet. The voltages to other parts are not correct also. Diodes check as Ok. At this stage I now have to replace all parts to find it as I WONT give up. Any ideas? Thanks Colin VK5HT Adelaide South Australia.
vk5ht
 
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Joined: Fri Dec 07, 2018 12:04 pm

Re: FT 767GX power supply 13.5v regulation problem

Postby vk5ht » Wed Jan 02, 2019 4:06 am

Hi

A follow up for the poor regulation. The mosfet Q7 2sk192 was faulty and has been replaced, I can now partially regulate the voltage but only to 15v. Still more to do,
vk5ht
 
Posts: 6
Joined: Fri Dec 07, 2018 12:04 pm


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