• Please note that there are a few updates and clarifications made in the Audiokarma Rules, mostly relating to advertising and the addition of the new "Paying it Forward" & "Giving back" forums in the AudioKarma Audio Marketplace section.

9090DB Fusible resistor replacement with regular fuses?

Jonathan75

Jonathan75

Active Member
Does anyone have a late production version of the 9090DB with fuses in place of the fusible resistors on the Power Supply Board? Pete gave me a heads up on that but I just need to find out what value fuse to use. I have some 5A Fast Acting fuses laying around with legs on it but not sure if that is too low or high?

With HomerJSimpson's help I found that R30 and R31 which are 1.0 ohm 1/2W Fusible Resistors that comes after the yellow transformer wires were totally open. I am hoping that after I replace them it just might start working. :music:

Radio Shack does not sell the resistors so I want to try the fuse route so I don't stall progress while I have time on the weekend.
 
Register to hide this ad
two 1.5 amp and one 1 amp fuse

I think these will work fine... two 1.5 amp and one 1 amp fuse. These are smaller than factory installed however should work. Make sure they are inside a plastic tube as original late production.
PM me and I will send you the three fusses if you don't have the amp value.
Peter
 

Attachments

  • STA72436.JPG
    STA72436.JPG
    145.7 KB · Views: 124
naderpe said:
I think these will work fine... two 1.5 amp and one 1 amp fuse. These are smaller than factory installed however should work. Make sure they are inside a plastic tube as original late production.
PM me and I will send you the three fusses if you don't have the amp value.
Peter
Click to expand...

I searched and searched for those fuses, what are the digi-key part numbers? I'm gonna order 20 of em, thanks!
 
Should be fine.

The plastic tube was probably so the fuses would not short to anything while they were hanging about.

A quick cheap mod Sansui made.

I have no troubles with my mod.

Rob
 
Now the agony of waiting for Radio Shack to open at noon on Sunday. Good thing the clocks spring forward tonight, one less hour to wait to see if my 9090 will come to life! :banana:
 
Looks like you got your answer regarding the fuse value. You can hack off two of those fuse holders to make that block a little smaller. You can probably mount it somewhere under the power supply so it doesn't look tacky with the top cover off.

- Pete
 
Well one step forward but two steps back. I rigged up some fuse holders by modifying some red wire caps with some 1/2 amp fuses and wire I had laying around. Now I get power to the tuner and I can see it tune a station! But..... now it won't come out of protect and the light flashes red. If I remove the fuses it will come out of protect and go green. I am open to any suggestions on what to check next.
 
Last edited:
For diagnostic purposes would it do any harm to remove the vertical standing board (F-2624 Driver Circuit Board) from the Power Supply Circuit Board? I wanted to see if with it removed it would come out of protection to possibly isolate the problem.
 
Jonathan75 said:
For diagnostic purposes would it do any harm to remove the vertical standing board (F-2624 Driver Circuit Board) from the Power Supply Circuit Board? I wanted to see if with it removed it would come out of protection to possibly isolate the problem.
Click to expand...

no prob at all. In fact this will tell us if the problem is the driver board or the outputs. I suspect the fuseable resistors that are on the driver board...
 
Check the outputs! There is a reason those fuseable resistors were fried. Also, you need to check the fuseable resistors on that driver board.

- Pete
 
Thanks Pete and Homer. I powered up the unit with the Driver Board removed and it came out of protection. So I checked every fusible resistor on the board and found some bad ones. Do I just replace them with new fusible resistors or is there another upgrade for this board also? Here are the results. Now I will check the transistors.

Bad R34 = 269 k ohms
Bad R33 = Open
OK R35 = 5.5 ohms
OK R36 = 5.2 ohms
OK R39 = 10.4 ohms
OK R40 = 10.2 ohms
Bad R41 = Open
Bad R42 = 39.4 k ohms
Bad R43 = 44.7 k ohms
Bad R44 = .978 k ohms
OK R47 = 5.3 ohms
OK R48 = 5.3 ohms
OK R49 = 5.2 ohms
OK R50 = 5.2 ohms

9090DB%20Driver%20Board%20Conductor%20Side.jpg


9090DB%20Driver%20Board.jpg
 
There are at least a couple of threads already describing x0x0db driver board refurbishing in some detail.

In short, the best option is to replace all of the fusible resistors with metal film resistors, and recap the driver board while you have it under the iron. For bonus points, you can upgrade the trim pots while you are at it.
 
As has been said, there is a ton of information on refurbishing those boards. Do a search. Metal film resistors are the way to go. The 180 ohm and 150 ohm fuse resistors are the usual suspects but it doesn't hurt to replace all of them.

- Pete
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom