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IN4148 in place of a IN34A diode?
- Thread starter daveyh
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Not really. The 1N4148 is a silicon diode and the 1N34A is a germanium diode.
Unless you can find some old stock 34A's ---NTE is your only resource.
damn ---to slow...
daveyh
Super Member
It is for the power supply board for a Sansui 881. No sound and the relay is not kicking in. I let a guy use it and he brought it back this way. The outputs check out to be OK. The service manual said check the 4 diodes D06~D10 on the F-2437 board. I did and they are open. I don't know what he did. I only have some IN4148's. I'll see if I can find some IN34A's.
daveyh
Super Member
I'll see i I can find some old stock. If not it looks like I am stuck with NTE for now.
The manual calls for 1N60's. Either the 1N34 or 1N60 is fine. But I'd be surprised if this was the root issue.
Measure the voltage at Pin #15 and Pin #18 on this board after checking
ALL the fuses (there's a bunch of them) ahd verifying that Pin #3 and #4 on the power amp driver boards have about 45V on them, and Pin #13 and #14 have about -45V.
Some of the schottky diodes have similar voltage drops as germanium, and could be used here. Germanium diodes can be found on lots of tuner boards if you have any dead units floating around. Check diodes before putting them in - on one old thread OP was having problems because one of the diodes he put in was bad. Good luck.
daveyh
Super Member
I have checked all the fuses. They are all good. DBT lights up dim and then goes down to no light at all (at least I can not see it). Have not changed the diodes because I did not know if you wanted the voltage before or after but here in the voltages I am getting if I am doing this right.
Voltage #15 and #18 = 39.8
" # 3 = 39.7
" # 4 = 39.9
" #13 = 79.8
" #14 = 40
daveyh
Super Member
I have some dead parts units. How do I know if the are the size Germanium diodes I need?
Parts lists in the service manuals for the parts units. Service and repair of vintage quite often takes a little research.
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daveyh
Super Member
Hey. Good idea. My common sense is faltering me as I get older.
daveyh
Super Member
Pulled the diodes off the board in question and rechecked. They are all good. Measuring them on the board gave me false readings. Would a burnt HA1149 IC keep it from clicking in the relay? Looks like it has gotten hot. I think I had one and these units before and seems like I replaced that chip because it was giving the unit problems. Can't remember why.
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I think you botched the reading @ #13.
It can't really be higher than the supply. And ALWAYS show units here...i.e., 39.8V or 39.8mV or 39.8 whatever, but label it!Anyway, #15 and #18 are the output of the two amplifier channels. If your reading is accurate and in VOLTS, both channels are blown, as you should be seeing something close to zero volts here (or at least under 100mV) when all is functioning properly.
daveyh
Super Member
I think you botched the reading @ #13.
Anyway, #15 and #18 are the output of the two amplifier channels. If your reading is accurate and in VOLTS, both channels are blown, as you should be seeing something close to zero volts here (or at least under 100mV) when all is functioning properly.
Well, I tried again and I can't get consistent readings like your post shows. So I guess I am going to have set it back for awhile and let my brain clear. I really do appreciate your help and one day I will pull it out and see if I can look at it again or take it to someone with more knowledge that what I have.
daveyh
Super Member
I have a new Craftsman AutoRanging Digital MultiMeter. Model 82139. Battery is new also. Maybe not the best meter to use but it is all I have. Maybe you can suggest to me a better meter? Maybe I am using the wrong setting? I tried in autorange, mA, DC and AC setting. Sometimes I get a reading that stops say at 37.9V in autorange and sometimes I get a reading that fluctuates up and down and never stops on a specific reading. Black grounded to frame and red on pin I am measuring. What am I doing wrong?
All the readings you are taking should be made with the meter set to 'VDC'. For any measurement taking I strongly recommend minigrabber leads: http://www.audiokarma.org/forums/showpost.php?p=2867400&postcount=10
Leads should be placed (or removed) with power off, then power is applied and the reading noted.
Leads should be placed (or removed) with power off, then power is applied and the reading noted.
All voltage measurements should be taken with the negative lead on the chassis, or on Pin #5 or #2 of the power supply board. I say this because you state that you have 30-something volts on #13, which should be more like 13V. Or maybe your board is different from what my manual says it should be, in which case we're pissin' into the wind here.
Please take these measurements again, with the negative meter lead on a good ground, and compare what you see with the values in the service manual.
Please take these measurements again, with the negative meter lead on a good ground, and compare what you see with the values in the service manual.
