Help with 8080DB
- Thread starter archie2
- Start date
Tinman
Super Member
That case looks great!! Mmmmmmmm.... wooooooood.....
Yes, the tuner comes out the top. Remove the 8 (I think) screws holding the chassis down. Then wiggle it out. Unplug cables, and watch for a black ground wire that plugs in under the tuner power board. Do NOT forget to plug this wire back in, either.
I had to lift and slide my tuner chass a little to get it out. There may also be a piece of tape that sticks the chassis down. Just gently work it out. It's actually simpler than it sounds.
Yes, the tuner comes out the top. Remove the 8 (I think) screws holding the chassis down. Then wiggle it out. Unplug cables, and watch for a black ground wire that plugs in under the tuner power board. Do NOT forget to plug this wire back in, either.
I had to lift and slide my tuner chass a little to get it out. There may also be a piece of tape that sticks the chassis down. Just gently work it out. It's actually simpler than it sounds.
kdillinger
Member
Well....actually....I don't think you need to remove the faceplate, or at least I never do on mine. There are two small counter-sunk screws on the top of the face plate that attach to the tuner chassis.
I always remove the tuner chassis screws and just tilt the rear of the tuner a little and it comes right out. The tuner knob has to be removed, obviously. Like mentioned previously, it really is no big deal to pull the tuner out.
Just make sure you have disconnected all of the misc. connectors and individual wires, including the previously mentioned black wire that connects to the bottom of the RF powersupply board (F-2619) . It is probably a good idea to take a photo of the tuner with the wires connected before you start, especially if it is your first time.
The unit will work with the tuner removed with the exception of the tuner of course and any Dolby functions.
I just successfully rebuild that board and am now enjoying the receiver completely.
I always remove the tuner chassis screws and just tilt the rear of the tuner a little and it comes right out. The tuner knob has to be removed, obviously. Like mentioned previously, it really is no big deal to pull the tuner out.
Just make sure you have disconnected all of the misc. connectors and individual wires, including the previously mentioned black wire that connects to the bottom of the RF powersupply board (F-2619) . It is probably a good idea to take a photo of the tuner with the wires connected before you start, especially if it is your first time.
The unit will work with the tuner removed with the exception of the tuner of course and any Dolby functions.
I just successfully rebuild that board and am now enjoying the receiver completely.
archie2
Addicted Member
I'm new at this so I need to confirm a lot. Here is the underside of the 8080DB tuner power board. I have boxed in what appears to me to be a cracked solder joint. Am I on the right track and should I reflow that joint? The crud on the cap is old glue ( I think).
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archie2
Addicted Member
I thought it had been tinkered with before. But previous tinkering aside, is that joint the culprit? And what are those copper tracings please?
nosirrah
RIP 11-19-2019
Joint
It well could be, did you probe each side of that damaged area with your meter set on OHMS to see if you even had continuity there?
Casey
It well could be, did you probe each side of that damaged area with your meter set on OHMS to see if you even had continuity there?
Casey
archie2
Addicted Member
Test probe give me a reading of 4 or 5 on a 1x scale.
kdillinger
Member
The glue on the cap could be remnants from prior tinkering. That cap on my board was mounted on the top side and had a vinyl tube sleeve over it, I'm guessing to help shield it from heat. When I removed the vinyl sleeve, the inside of the tube and the outside of the cap has this glue on it. So I guess it is possible the cap was either on the top side or had a vinyl sleeve over it at one point in time.
The copper traces on your board under TR-01 appear to of been worked on in the past. This is the typical failure area on this board. It is possible that the pad (the circular area where the leg of a transistor, resistor, diode, etc. solders to) has lifted from the circuit board wafer material. If so, you will have to make a significant repair to the board. I would also check the continuity to the next component in the circuit. If the traces are intact then reflow should work. If not, the you will have to recreate the trace with wire.
It looks like some of the varnish was scraped away to either get a clean surface to solder to or to get a clean point to check with a meter probe
Good luck. You can refer to a picture I posted earlier in another thread for the repair that I had to make, which appears similar to the repair you may have to make. I would caution that if the board does need an overhaul, it may not be do-it-yourselfer depending on how well you understand schematics.
The copper traces on your board under TR-01 appear to of been worked on in the past. This is the typical failure area on this board. It is possible that the pad (the circular area where the leg of a transistor, resistor, diode, etc. solders to) has lifted from the circuit board wafer material. If so, you will have to make a significant repair to the board. I would also check the continuity to the next component in the circuit. If the traces are intact then reflow should work. If not, the you will have to recreate the trace with wire.
It looks like some of the varnish was scraped away to either get a clean surface to solder to or to get a clean point to check with a meter probe
Good luck. You can refer to a picture I posted earlier in another thread for the repair that I had to make, which appears similar to the repair you may have to make. I would caution that if the board does need an overhaul, it may not be do-it-yourselfer depending on how well you understand schematics.
archie2
Addicted Member
It looks to me that the traces are broken at one of the heat sink anchor points (see red circle) and was chipped off by a very loose heat sink. I'm thinking I have to make a trace with wire from point to point as per the black arrows. This matches the power board schematic I printed off your repair thread.
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kdillinger
Member
That looks basically correct. You should still pick-up the heatsink in the circuit. I've included a pic of my repair that worked just fine. I have to admit, the photo has one error. I soldered one of the wires to the wrong pad. I marked the correct location on the picture. Luckily, I caught the error before I powered up the board.
On my board, all 3 of the pads for TR-01, as well as the heat sink mounts were shot. Since this area gets very hot, I elected to run wire for all 3 legs of TR-01 and be done with it.
You could read thru this thread, you might find some info useful http://www.audiokarma.org/forums/showthread.php?t=198087
On my board, all 3 of the pads for TR-01, as well as the heat sink mounts were shot. Since this area gets very hot, I elected to run wire for all 3 legs of TR-01 and be done with it.
You could read thru this thread, you might find some info useful http://www.audiokarma.org/forums/showthread.php?t=198087
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archie2
Addicted Member
kdillinger
Member
Actually, I just used 2 layers of heat-shrink tubing on the wire leads that I soldered to the transistor and heat-sink.
Another thing that you can't see, I made the modification of re-locating the big resistors. I used one single wound resistor and mounted it to the chassis to help remove some heat from the board. I read about the mod. on this forum and figured it couldn't hurt since I already had the board out.
Let us know how you make out.
Another thing that you can't see, I made the modification of re-locating the big resistors. I used one single wound resistor and mounted it to the chassis to help remove some heat from the board. I read about the mod. on this forum and figured it couldn't hurt since I already had the board out.
Let us know how you make out.
kdillinger
Member
After looking at that board diagram and at your board, I think the board diagram is more like my board than yours. I think yours is a newer version that is not completely reflected in the diagram . If you notice, I have a connector on my board for the black wire to connct to (near a screw). I did not see this on your board. However, that location is shown on the diagram. Also, next to the variable resistor, there are 2 fixed resistors (R-05 and R-06), the diagram looks more like my earlier board. Looking them over though, you can see they are basically the same. R-01 and R-02 are the resistors that can be relocated and combined.
Here is a pic of the actual schematic of the board in circuit if it helps any
http://www.audiokarma.org/forums/attachment.php?attachmentid=124112&d=1229656116
Here is a pic of the actual schematic of the board in circuit if it helps any
http://www.audiokarma.org/forums/attachment.php?attachmentid=124112&d=1229656116
archie2
Addicted Member
I see your black wire prong connector and the single wound resistor repositioned on your other thread. I don't see a cap (area circled in black) where mine is. Did you reposition that? I'm going to look at the schematic more closely because your rewired pic looks different from the wire bridge I was proposing on my board.
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kdillinger
Member
As I mentioned earlier, my cap is on the top side of the board. Sansui later re-positioned the cap to the bottom of the board to get it away from the heat.
The bridge you propose should work just fine. I connected my heat sink to the other resistor (R-01 and R-02 are parallel). On my board, the trace from the center lead of TR-01 was also shot so I connected it to the resistor that you point to in your picture. Both connections are the same since the resistors are in parallel. This way, I didn't have to try to get 2 wires soldered into one joint, I split them up.
Connecting a wire from your heatsink mount to either R-01 or R-02 is the same. If you look at the trace, it is common to one end of both resistors.
The bridge you propose should work just fine. I connected my heat sink to the other resistor (R-01 and R-02 are parallel). On my board, the trace from the center lead of TR-01 was also shot so I connected it to the resistor that you point to in your picture. Both connections are the same since the resistors are in parallel. This way, I didn't have to try to get 2 wires soldered into one joint, I split them up.
Connecting a wire from your heatsink mount to either R-01 or R-02 is the same. If you look at the trace, it is common to one end of both resistors.
archie2
Addicted Member
Much obliged for all your help. I'll let you know how it turns out.:thmbsp:
archie2
Addicted Member
Well, I screwed up already, sort of. I took pictures of the wiring before I started, unfortunately in an attempt to maneuver the tuner board for better stabilization I pulled off some connections that the camera did not catch. I think, but not 100%, I've got I and II figured out correctly to their matching male connections but I don't know where III goes, III is the smallest one with the black wire. 
