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The OFFICIAL MSM5540RS/M5540 Sansui Gx700 40pin IC Thread! NUDIES

seeing as F-3220 seemed to have replaced f-3000, I am tending to think it was an effort to consolidate both boards and fold it into one....

and I googled the heck out of F-3220 just to find my own posts about it, here on AK,...

I traced the cable connectors out of F-2988 (radio board) and they both feed into either side of F-3220.
 
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If you have F-3220 then I consider it very likely that the two sections have been amalgamated. This kind of display assembly was used extensively across Sansui receivers and tuners, so updates would have been commonplace. Guessing here the the F-3220 is an updated F-3000 board - but I can't find any reference to the F-3220 board.
 
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only thing i see with that amagamation is that I can no longer see where the scaler board fits into the picture. None of the ICs on F3220 match up with the ICs on the former scaler board...
 
IMG_20150206_135930.jpg


IMG_20150206_135944.jpg


and here you can trace the wire bundles leaving 2988 right into 3220..

IMG_20150206_140032.jpg
 
I can't find a schematic for the F-3220 board. You can trace the wiring on the board from the connectors and look for caps. If you had a scope you could save yourself a lot of trouble.
 
dr*audio said:
I can't find a schematic for the F-3220 board. You can trace the wiring on the board from the connectors and look for caps. If you had a scope you could save yourself a lot of trouble.
Click to expand...
You might be able to find a working Tektronix 465 for $75.
 
im at a serious crossroads if i should invest in any diagnostic equipment as this is blowing my mind.

BK king and i are working offline and it seems my unit doesn't have a scaler unit, OR pins 27/28/30 that could come off of the display board.. so basically nothing to accommodate for the scaler..

so now the question is.. how do the units with the f-3220 operate without the scaler........???
 
trueno92 said:
im at a serious crossroads if i should invest in any diagnostic equipment as this is blowing my mind.

BK king and i are working offline and it seems my unit doesn't have a scaler unit, OR pins 27/28/30 that could come off of the display board.. so basically nothing to accommodate for the scaler..

so now the question is.. how do the units with the f-3220 operate without the scaler........???
Click to expand...

It does seem like it can't operate without it, maybe there is another updated(?) board in the receiver that is paired with the F-3220 that you have that incorporates the scaler on it ? - more guessing... :(

Just FYI - There is a lot more information on circuit operation in the TU-719 manual which uses the same display, might be of help to track down the fault you now have - but having a 'scope (and knowing how to use it) will help a lot.

And...
http://www.audiokarma.org/forums/showthread.php?t=318875 - see post #9
 
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How about a newbie suggestion, a question rather. How are your Peak Power Level lights doing? Mine are connected to scaler board, sharing connections with digital display board, without my digital display board, these lights just stayed at the peak level. So assuming your lights share the principle, maybe there is a couple of wires from PPL to scaler area on the other board?
 
as suspected, the scaler is onboard the F3220...

it checks out voltage ok.. but output i am not entirely sure.. so... now its a broken scaler.. or input getting to the scaler........ or output from the scaler.......


and i have to wait a whole 10 more months to ask for a F3220....
 
I've been working on this most of the afternoon. I need the datasheet for that 40 pin chip. AM and FM frequencies are independent from the each other, therefore the scaler only works for the FM frequencies. Something is pinning the display, it's not the scaler- we tested voltages and they look to be correct. At this point i'm thinking crystal as warren says.

Digikey sells the crystal for 70 cents, shame it's going to cost $8.00 to ship it!
 
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Brad has blown my mind today with a cram class in component-level troubleshooting. Its much appreciated and as a result has questioned my capability in resolving this! on the F3220 surprise, the scaler is in fact onboard. Neat stuff so as was suspected - the F3010 was consolidated to a single board.

Now for the crystal, im guessing that if i swapped in another, i should get the display to scroll. it would be off but at least it would move, no?

also, the crystal is right off of pin 39 on the MSM5540 chip, and our guess is the old MSM5540 shorted and took the crystal out with it...

is the jury convinced? I have read that crystal oscillators can fail and heck, 30 yrs old and a chip throwing a curve ball and i guess its certainly possible..?
 
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http://www.digikey.com/product-detail/en/ECS-65-12-1X/X977-ND/827469

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HC-49U_sml.jpg

?????????????????????
 
That block diagram is somewhat deceiving, the IC's on the prescaler make up the FM portion, the AM is simply a couple of transistors.
 
Looking at the voltages on the prescaler isn't enough to tell if it's working or if you have a signal going into and out of it. The output of the prescaler is the frequency of the LO / 100, so on the order of 1MHz. It is not a DC voltage. You need a scope.
 
bktheking said:
I've been working on this most of the afternoon. I need the datasheet for that 40 pin chip. AM and FM frequencies are independent from the each other, therefore the scaler only works for the FM frequencies. Something is pinning the display, it's not the scaler- we tested voltages and they look to be correct. At this point i'm thinking crystal as warren says.

Digikey sells the crystal for 70 cents, shame it's going to cost $8.00 to ship it!
Click to expand...

How did you conclude the prescaler is ok, without being able to look at the signal with a scope?
 
Voltages measured within spec and the chip wasn't hot. In the end without a scope it was a guess and a good guess at that. Just to update , he installed a 6 MHz crystal last night and the display now works albeit the correlation between scale and digital is off. He's going to get the proper crystal this week which should solve the issue.
 
I'd say that's pretty unusual to lose the crystal - but hey! - sounds like progress is being made. ;)
 
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