resi.studios
Member
So I have been gifted this unit along with a 2280 and a MCS 3260. All three were not working correctly. I did major repairs to the 2280 and got the 3260 going. This 2290 however is a basketcase. I have done my fair share of restorations in the past few years (150+) but this one is taking me for a ride and I am at wits end.
Probably 30+ Delcon caps and another brand that were coming apart, at the leads or just expelled its electrolyte (which is dried) who knows how long ago. Corrosion everywhere (and no, I am not talking about the glue staking the caps to the PCB.) I am not sure what this thing went through but I believe it was outside, as there was sand all up in it. I already blew it out and cleaned what I could.
It has 3 shorted outputs, which was to be expected. However, there is another issue that is preventing me from buying the outputs and moving onto the amp board to verify/check drivers etc. Pretty routine stuff but if the display /front panel doesnt work it renders the unit unuseable.
The display , actually the whole front panel lamps, have this issue where they come on upon a cold start and then they slowly power down and go dark. I have traced this to a power supply issue - HOWEVER - I have a WORKING 2290 and I swapped the whole power supply PCB (2 boards) and it did the SAME THING. I have been trying to interpret the schematic and slowly go through every component that would be an easy target (i.e. the delcon caps). There is a green reed relay which seems to be a part of the circuit, I replaced it too with a modern OMRON G5V-2-H1 (dead bug style) because I have had major issues with them in the past.
I have unplugged the speaker relay, amp boards, and the display board to rule them out affecting the circuit. There is a STRONG 57v or so I believe at the main filter caps (which are new). Actually, upon start up the lamps are now quite bright (but then shut off after about .5 of a second.) There is this reference voltage that I have been tracing but the design is difficult to understand for me. The voltage that keeps the lamps on can be measured in several different areas, it seems to "start" at pin 4 of the power supply PCB upon a cold start. Its like a basic 13-15v supply, that seems to go everywhere.... on the good 2290 it holds a solid 13+ volts, on the bad unit, on every junction it quickly drops to 2 volts. Its almost like there is something that is causing the voltage to get pulled down and collapse. I have replaced EVERY capacitor and double checked polarity etc compared to the working 2290. It would seem the power supply boards are supplying that voltage but they are infact not supplying 13v directly there, because when the connector is removed it simply reads 0 volts. So the power supply is working in tandem somehow with another area in the unit to manage a secondary supply voltage for the display/ lamps etc. But the main power supply boards as listed in the schematic dont seem to be the culprit. This is how it seems to me but the schematic is difficult for me to understand and unless I am reading it wrong its not stating voltages.
Here are some pics that I took of where I measure that voltage that drops when the display power down. You can literally see it drop... even with the whole front boards etc removed (there are two).
Here is the pin, pin 4 that goes to the power supply board, that reads 0 when unplgged and drops shortly after unit is turned on. This is what made me feel like it would be an obvious place to check but swapping the boards resulted in the same issue.
This supply voltage goes through a certain area on the same board the FM section is that is notated as the TUNER / IF/ MPX . This is where the relay is located
The voltage needs to be stable but I feel like I have verified the actual power supply section at this point. I think its taking some voltage from somewhere I am not seeing and regulating it somewhere else but I dont know where and I cant seem to understand where.
I am thinking maybe there is a cap that is shorted pulling everything down but before I start removing more I would like to see if anyone can take a look so I can save this unit. I also noticed there are some pots on the FM section that have the words "METER" etc but I believe they are related to the FM section and not power-regulation. I could also be simply overthinking this and just need a second man's eyes on it.
The schematic is here at AK AK Database PDF Gallery - Realistic/Realistic STA-2290 Schematics
Thanks.
Probably 30+ Delcon caps and another brand that were coming apart, at the leads or just expelled its electrolyte (which is dried) who knows how long ago. Corrosion everywhere (and no, I am not talking about the glue staking the caps to the PCB.) I am not sure what this thing went through but I believe it was outside, as there was sand all up in it. I already blew it out and cleaned what I could.
It has 3 shorted outputs, which was to be expected. However, there is another issue that is preventing me from buying the outputs and moving onto the amp board to verify/check drivers etc. Pretty routine stuff but if the display /front panel doesnt work it renders the unit unuseable.
The display , actually the whole front panel lamps, have this issue where they come on upon a cold start and then they slowly power down and go dark. I have traced this to a power supply issue - HOWEVER - I have a WORKING 2290 and I swapped the whole power supply PCB (2 boards) and it did the SAME THING. I have been trying to interpret the schematic and slowly go through every component that would be an easy target (i.e. the delcon caps). There is a green reed relay which seems to be a part of the circuit, I replaced it too with a modern OMRON G5V-2-H1 (dead bug style) because I have had major issues with them in the past.
I have unplugged the speaker relay, amp boards, and the display board to rule them out affecting the circuit. There is a STRONG 57v or so I believe at the main filter caps (which are new). Actually, upon start up the lamps are now quite bright (but then shut off after about .5 of a second.) There is this reference voltage that I have been tracing but the design is difficult to understand for me. The voltage that keeps the lamps on can be measured in several different areas, it seems to "start" at pin 4 of the power supply PCB upon a cold start. Its like a basic 13-15v supply, that seems to go everywhere.... on the good 2290 it holds a solid 13+ volts, on the bad unit, on every junction it quickly drops to 2 volts. Its almost like there is something that is causing the voltage to get pulled down and collapse. I have replaced EVERY capacitor and double checked polarity etc compared to the working 2290. It would seem the power supply boards are supplying that voltage but they are infact not supplying 13v directly there, because when the connector is removed it simply reads 0 volts. So the power supply is working in tandem somehow with another area in the unit to manage a secondary supply voltage for the display/ lamps etc. But the main power supply boards as listed in the schematic dont seem to be the culprit. This is how it seems to me but the schematic is difficult for me to understand and unless I am reading it wrong its not stating voltages.
Here are some pics that I took of where I measure that voltage that drops when the display power down. You can literally see it drop... even with the whole front boards etc removed (there are two).
Here is the pin, pin 4 that goes to the power supply board, that reads 0 when unplgged and drops shortly after unit is turned on. This is what made me feel like it would be an obvious place to check but swapping the boards resulted in the same issue.
This supply voltage goes through a certain area on the same board the FM section is that is notated as the TUNER / IF/ MPX . This is where the relay is located
The voltage needs to be stable but I feel like I have verified the actual power supply section at this point. I think its taking some voltage from somewhere I am not seeing and regulating it somewhere else but I dont know where and I cant seem to understand where.
I am thinking maybe there is a cap that is shorted pulling everything down but before I start removing more I would like to see if anyone can take a look so I can save this unit. I also noticed there are some pots on the FM section that have the words "METER" etc but I believe they are related to the FM section and not power-regulation. I could also be simply overthinking this and just need a second man's eyes on it.
The schematic is here at AK AK Database PDF Gallery - Realistic/Realistic STA-2290 Schematics
Thanks.