TP voltages on FG085 Schematic ?

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Posts: 1
Joined: Wed Dec 16, 2015 3:44 pm

TP voltages on FG085 Schematic ?

Post by aneng »

Hi, I'm trying to repair my FG085 (revision 'G') after I stupidly connected the power supply up in reversed polarity :roll: I have already replaced several components that had blown; C4, U3 & U1 but I could do with having a list of the Test Point voltages / waveforms to help me pin down the fault.

I am assuming that as there are many Test Points indicated on the schematic ( that there must be a list of correct voltages or waveforms to match.

Would JYE be able to help please ?

Thanks !
Posts: 1221
Joined: Wed Feb 20, 2013 4:58 pm

Re: TP voltages on FG085 Schematic ?

Post by jye1 »

Power supply:

Here are the correct voltages for power supply (assuming +15V power supply is used).

TP12 (+5V) ---- +5V
TP13 (V-) ---- about -13V
TP14 (V+) ---- about +14V

Ignore TP17 which is not used.

Once you have +5V correct you should have both micro-controller running. Keypad and display working.

Signal generation circuits:

TP15 directly reflects OFFSET setting.

TP21 is the output of DAC. Its waveform is the selected waveform, with 10Vpp amplitude and 0V offset.

TP20 is final output that combines attenuated amplitude and offset.
Posts: 1
Joined: Sun Feb 14, 2016 10:56 am

Re: TP voltages on FG085 Schematic ?

Post by ivsto »

I had the same problem...according me DB1 is missing. It's stupid to lost FG085 for a few cents..
I changed U1 and it's OK!
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