Realistic STA-2250 receiver

968driver

New Member
Hi,
I have a problem with a Realistic STA-2250 receiver.
After power off, all stored presets of the tuner are cleared everytime.
I do not find a memory backup battery or capacitor in this unit.
I also do not have a schematic.
Any suggestions?
Kind regards, 968driver.
 
Is your method of power-off to hit an external switch, as on a power strip, as opposed to using the unit's own switch while the power cord remains live?
 
Realistic STA-2250 AM/FM receiver

I use the power switch of the unit.
The receiver is always connected to the mains.
If I switch it on again within 10 seconds, presets are still present, after about 10 seconds all presets are cleared.
All other functions of this receiver work!
 
When you say "mains" you are talking about the wall A.C. correct? Assuming you literally sit/stand there and turn it off and then wait 10 or more seconds and turn it back on, then yes you have a Cap/Battery issue. I've looked through almost a dozen RS catalogs and can't find your receiver. What is the catalog number on the back?
 
when you say "mains" you are talking about the wall a.c. Correct? Assuming you literally sit/stand there and turn it off and then wait 10 or more seconds and turn it back on, then yes you have a cap/battery issue. I've looked through almost a dozen rs catalogs and can't find your receiver. What is the catalog number on the back?

1981-83
 
Realistic STA-2250 AM/FM receiver

The model number on the back of the STA-2250 is: 31-2095.
Could this be the catalog number?
There is a big and a small power transformer inside. For a moment I supposed the small one is the stand-by transformer and this could be defective.
However, this is not the case. When I disconnect the small transformer, the fluorescent digital readout is dark.
So the small transformer is O.K.
What I really need to solve this one is a schematic.
Thanks for any help!
 
The model number on the back of the STA-2250 is: 31-2095.
Could this be the catalog number?

Yes, that's the catalog number.


What I really need to solve this one is a schematic.
Yes, a service manual would help, but couldn't locate one.
Maybe someone else here has one.

Can you post some good quality pics of the microprocessor area?
 
I would think if there was a battery/cap for presets it would be located on the tuner board. I'll check my STA-2250 tonight.
 
I would think if there was a battery/cap for presets it would be located on the tuner board. I'll check my STA-2250 tonight.

Thank you,
He said he checked and there wasn't one present, but
something has to be there to hold the memory.
 
Realistic STA-2250 AM/FM receiver problem solved!

Hi,
today I fixed the problem without having the unoptainable service manual.:yippy:
In this receiver, there is no backup battery and no backup capacitor.
However, on the microprocessor board, there is, near the microprocessor, a 1000µF/10V elco.
When desoldering this elco, one of its wires was disconnected from the body (apparently by some chemical action).
Visually, nothing was giving a clue to this situation.
After replacing this elco, station memory is sustained.
On the same board, I replaced another 1000µF/10V elco, the value being decreased to about 100µF.
I also replaced some other elco's.
Visually, nothing seemed to be suspected. No bulging, no fluids escaping.
To me, it seems to be that the elco's in this receiver are not high quality types. It is my experience that quality Japanese audio gear does not suffer from bad elco's, even after 30 years!
 
Hi,
today I fixed the problem without having the unoptainable service manual.:yippy:
In this receiver, there is no backup battery and no backup capacitor.
However, on the microprocessor board, there is, near the microprocessor, a 1000µF/10V elco.
Good deal :thmbsp:
Apparently they used non volatile memory (eprom probably).
The bad caps you found were keeping the processor from writing
to the memory.

When desoldering this elco, one of its wires was disconnected from the body (apparently by some chemical action).
Visually, nothing was giving a clue to this situation.
After replacing this elco, station memory is sustained.
On the same board, I replaced another 1000µF/10V elco, the value being decreased to about 100µF.
I also replaced some other elco's.
Visually, nothing seemed to be suspected. No bulging, no fluids escaping.
To me, it seems to be that the elco's in this receiver are not high quality types. It is my experience that quality Japanese audio gear does not suffer from bad elco's, even after 30 years!

At some point you will probably need to do a full recap of the unit.
 
sta-2250

i have 2 of these units myself, i totally re-capped them both and the difference is astounding, one ive had from new the second i purchased as a re-build project, apart from the recapping and adding some multi-turn vr's to fine tune the bias on the amp board ive had to do nothing else they perform like gems :)...i do have the service manual for this amp, and will be happy to scan and post it if theres still interest in this unit .:music:
 
sta-2250

thnx for the welcome :D, ill post the manual soon as ive scanned it then, its in mint condition so should make a good copy.....i personally wont buy any equipment bar none if i cant get a service manual with it , one day be it 20 plus years later they sure come in handy
 
I just purchased a STA-2250 from Ebay for $20 plus $40 shipping. Output was a little low on the right channel, a recap of the power amp board fixed that issue. I like the way the left and right inputs from the preamp section are in plain view, this enabled me to do some quick troubleshooting [preamp vs power amp].
Now I am looking for a manual or schematic. I would like to double check the bias settings on the output transistors. Also the memory's are not holding, I am going to replace those capacitors suggested earlier in the thread [Thanks for that info].
Any additional info appreciated. Yes I will eventually replace all those darn electrolytics.. :)
 
Hmmm. Dennis57, on previous page, said he had the manual you need, but i don't see it in the AK database yet. I've PM'd Dennis to see if he uploaded it or not yet.
 
hi guys, sry ill have it uploaded soon as i can :)


* memory not holding try replacing C827 (4700uf 10v) on the controller board :) (its the largest cap on that board)
 
* idle current .......adj voltage across emitter resistors R541(VR501= LCH) & R542(VR502=RCH) to 10mv +/- 2mv (8 ohm Load),


* selector switch set to aux

* mode set to stereo
 
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STA-2250 info Thanks!

Thank you very much for the information on idle current and memory storage cap. I will do my part also and scan and upload a copy of the SA2000 and TM1001 service manuals.

Regards,

GC
 
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