ft-102 display bad number

[seb5347]

hello
I m restoring a ft-102, lot of issue, had 24v to 12v regulation bad 2sb705 and 2sa733, i have repair the power supply. 12v ok now
The failure concerns all the digits.
0 is ok
1 is ok
2 is ok
3 is bad (one segment too many)
4 is ok
5 is bad (one segment too many)
6 is ok
7 is ok
8 is ok
and 9 is bad (one segment too many)
Any idea? main processor or other dead circuit (5066??)
Thanks 73's SEB F5SSL

[kellys_eye]

The circuit diagram seems to indicate the display (VFD) to be matrixed (digit and segment) but there is no 'common' fault as would be normal with a dodgy segment or digit driver issues therefore I can only assume the display itself is at fault.

[Cobaltblue]

Is it segment e that's extra to 3 5 and 9?

or different segments?

Cheers

Mike T

[Jon_G4MDC]

I read it like that Mike. Originally I thought seg(e) had a leak from seg(a) but that is debunked by a 7. It lights seg(a) but there is no corresponding unwanted seg(e).

Apart from that they follow the same pattern and a leak between them might have explained it...

Maybe I went wrong somewhere with my table?

[Cobaltblue]

I was tying to ascertain if when a wrong segment came up it was always the same segment if so I suspect problems withing the driver circuitry but as you say you would expect it always to appear in all numbers.

We can only await the OP's response.

Cheers

Mike T

[Radio Wrangler]

The counter chip in the FT101ZD is unobtainable. This may be the same.

David

[SiriusHardware]

Service manual can be found here:-

http://www.iw2nmx.it/Yaesu/FT-102/FT...e%20Manual.pdf

The counter / display circuit is on PDF page 58. I notice there are 3 x TC5066 ICs between the 'Big' counter IC and the display itself so one thing you could try, if those ICs are in sockets or can be socketed easily, is to circulate those three ICs through different positions to see if that makes the nature of the fault change. If it does, at least one is probably faulty.

First though we need a better description of the fault as it is not currently clear whether the OP was referring to displayed DIGITS 3, 5, 9 having one extra segment lit or whether he meant display CELLS 3, 5 and 9.

[PJL]

This is a fun puzzle...how about if d is on then e is on?

[Jon_G4MDC]

That seems to be a better one that I missed!

It's pretty clear from the manual just linked that one TC5066, Q08, is just concerned with mode annunciators - it connects to the mode switch wires. I suppose it has CW LSB etc shown in the display then.

That means the other two, Q9 & 10, must be multiplexing digit and segment for the numeric positions. I see diodes too.
I have a TS130V, also equipped with a VFD, where a problem like this was caused by a leaky diode.

Replacement cured the problem and no exotic chips needed to be found.

[SiriusHardware]

It does seem to be a design with 'too many diodes'.

[Jon_G4MDC]

Can see a little more now I have looked at it longer.

Q10 has seven connected outputs so that is the segment driver. It or a shorted track going to / coming from it are most likely to blame for seg(e) lighting when it shouldn't. Suppose it could also be a faulty Q07, the TC5070. Meter checks should reveal which it is.

Segment connections are

TC5070----------Q10 inputs---Q10 outputs
Pin 5 Seg(a)-----Pin 1---------Pin15
Pin 6 Seg(b)-----Pin 2---------Pin 14
Pin 7 Seg(c)-----Pin 3---------Pin 13
Pin 8 Seg(d)-----Pin 4---------Pin 12 Suspect shorted with Seg(e) maybe?
Pin 9 Seg(e)-----Pin 5---------Pin 11
Pin 10 Seg(f)----Pin 6---------Pin 10
Pin 11 Seg(g)----Pin 7---------Pin 9


Q09 has six outputs connected which is logical since the display employs 6 digits. If it's not a digit problem maybe leave this alone. The diodes seem more associated with this IC - probably related to getting the decimal point to light in the right place.

[seb5347]

Hello
First of all thank you all for your help. And bravo and congratulations Jon, the failure was of course on Q10!! I had a recovery IC on a ts-120s display board. I bracketed Q9 and Q10 and swapped out the ICs to see which one had the problem.
So after replacing Q10 everything is ok. See you soon and 73's from F5SSL

[Jon_G4MDC]

Very good. That's another one fixed.
73