I know this is an old thread but I've dug it up a few times this week as I've been busy transplanting a 9090DB tuner PCB into a regular 9090.
The stock tuner PCB was shot and botched with trails lifting, missing pads, epoxy gluing and too many jumper bypasses. I had a spare 9090DB
tuner PCB which I saved for a case like this. The good news is, it's doable and I thought I might share, so here's some pointers...
First of all, the 9090 none DB has the daughter piggy back F2550 Multi-Path PCB riding on it so it's infrastructure needs to installed:
Second, the 9090DB tuner doesn't distinguish between FM Auto and Dolby FM as everything is routed to the dolbey board. The none DB version
has two different FM outputs, "auto" and "dolby". Third, there's a whole bunch of ceramic caps and resistors in the AM section of the 9090DB tuner that are
not the same as the 9090 none DB. I'm not sure how critical these are, but I've swapped them to match the 9090 SM.
Here's a 9090DB tuner and the missing connection posts that come down the MPX daughter PCB are marked in yellow
To adjust this board to the 9090 none DB version, I've done the following:
- installed the MPX PCB Molex footer
- installed the three posts
- added resistor R98 (3.3KΩ)
- installed Germanium diodes D05/D06
- replaced the 0.0022µF ceramic cap (red 'X') with 0.022µF and re-oriented it (like plus to minus instead of diagonal)
- Resistor (R83 3.9KΩ was different on the 9090DB tuner)
- Possibly matched some ceramic caps in the yellow square near the AM tuner IC, as per the 9090 SM (sorry, I don't remember all of it by heart and didn't take notes on this one)
- Replaced AM tuner HA1197 with HA1152 (the HA1197 still works after the transplant though)
The transplanted tuner conductor side now looks like this:
The component side, like this:
During the transplant I had great AM reception but the FM was dead. Based on the trouble shooting guide I've checked TR-01~TR03, and the TO01/02 inductors,
I then continued to check the coils, transistors and FET on the front pack. I used the opportunity to give it a complete IPA bath and scrub. Notice how dirty the thing was (it's not water):
After the rinse, I could recap some of the smaller values ceramic caps with MLCC's and verify the values of the other CC's. Interestingly, none of the 0.022µF
CC's kept their values. They all drifted up to 0.03uF and higher, way over their tolerance. I replaced them with good 0.022µF caps.
The variable capacitor was cleaned too and the shaft gear greased:
Opening the dang thing was nearly impossible with my 15watt iron. I think they used led instead of solder. In the process I damaged some of the ground trace on the PCB
and I had to fix it later to create good solder anchors to the case.
Now it's all cleaned up and looks like this:
The transplant worked although I'm still debugging an issue. I get very good AM reception and very good FM reception. My stereo indicator lamp is missing, but my DMM shows the voltage out of TR09 in stereo mode. The only dang problem is my FM auto and FM dolby output is so low, I need to crank up the volume to max in order to hear it. My AM tuner works fine so if I'm not careful and switch to AM from FM, I get the full might of the 9090 through my bench speakers. Not cool! Luckily my DBT saved those speakers. I'm still working on it but I'm pretty sure I messed some connection in the tone control boards. I temporarily hacked this (power supply issue) and got FM, but it ain't totally right yet. I may need your guys help later on with this. Thanks for reading.