9090DB setting bias didn't go so well

First, I made a mistake above with the transistor number. The TO-92 reported as bad is not 1364 but 1211. I have edited the post to reflect this. How do I know. Well I put the working transistor back in the board before pulling the next TO-92 and that one is still out and it is the c1211. Interesting that both the 1364 and 1211 can be replaced with the same KSC2690. Seems the C1383 and C2310 are both out of print.

Caps checked and no shorts on them. The zener did the 0L and .58something IIRC. What I expected to see. On the board it climbs to .578 and reversed it climbs past 1V to 0L. I'll check the resistors while I put together a list for my parts source. The trimmer does work.

At least we are making progress. Thanks for all the help.
 
Be easier to replace it. AK says this is a ½-watt 5.6 V zener and well mouser has one for 39 cents. Might as well. Easier than rebuilding the board with the new transistors and then measuring the zener and having to replace it. And the 1-watt is only 26 cents.

Parts needed
MJE-15032
KSC2690, maybe two to replace both the C1211 and C1364
1N4734A
Any resistors, I need to measure
and all the parts for other projects.
 
Tarior: A scope alone may not help much in this case, but a scope to display the patterns from a component tester would be very helpful. I'm guessing that you have never seen one.
 
I have a nice curve tracer. I never use it. I can usually figure what's going on in a circuit way faster with just a DMM than I can set it up.
 
The nice feature of this type of curve tracer is that it enables you to view a waveform of the electrical conducting characteristics of a component(s) or circuit between two points, WITHOUT having to remove any components. Some waveforms are definitive indications of a failure, and sometimes you have to compare waveforms between the same points in the left & right channels. The main point is that it works.
 
Like an octopus,or a Huntron Tracker?
I have been kicking around the idea of buying one of those.
 
Did some more research on parts since I need some 1845s and Mouser doesn't have them yet and Digikey doesn't have some things I need on this next order.

Looking at those transistors again, I'll copy kdillenger's format for information as that could help. He did these parts replacements back in 2008.

I.D................Vceo...Ic........Pc,W......B(hFE).....Ft
TR-01 2SD313
2SD313...........60.....3.........30........40.........8.0
TIP41B............80.....6..........65........30........3.0
TIP41C..........100.....6..........65........30........3.0
KSC880..........80.....3..........30........60........3.0

TR-02
2SC1211.........65.....0.550.....0.500.....90-180...130
KSC2383........160....1.0........0.900.....60-320...100

TR-03
2SC1364.........50.....0.200.....0.320.....200........140
KSC945G........50.....0.150.....0.250....200........300
KSC2690........120....1.2.........1.2........140.........155
KSC815(Y)......45.....0.200.....0.400.....40-400....200

Learning about this, I think I would pick the KSC880 for TR-01 and the replacements listed for the others.
The only spec that isn't good enough is maybe the collector current for the first TR-03 substitute and the gain for the second. The third substitute is the one selected I believe. Board voltage even the incoming maybe 51V shouldn't ever get to TR-03 with the 5.6k resistor in front of it. Any recommendations?
 
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When you are testing the tuner power supply voltage, the wire that powers the tuner is connected? It must be.

Rob
 
Next time it is tested it will be. For the pennies that these parts cost and the hassle of pulling the board and putting it back in, I'm gonna swap the transistors (two measured bad out of circuit) and the zener, finish rebuilding the board and get it a test.
 
Parts are in and I got the Tuner PS rebuilt and adjust to 12.6 I guess. This is causing a good bit of heat in the 270Ω resistors and TR01. The voltage after the resistors is 33.5. The new diode has 5.4 V across it.

I want to install the 300Ω resistors I got, nice 10W units to drop the PS voltage a notch and try to keep TR01 from overheating. Any reason not to?
 
Well I put in the two 300Ω resistors and wall mounted them (that metal plate between the tuner section and the amp transformer area) to keep their heat away from the heat sinked transistor on the tuner PS board. Drops incoming voltage from 53+ to 27 and the vr drops it to a good number whatever that is. The scat show 12.5 but it is written above that it needs to be more. Fine. It is more.

Got temps and the resistors (10W) are running about 130°F and the transistor heat sink is about 80°. I am much happier with this than the 260° on the resistor behind the heatsink and something too high on the sink.

Getting this thing dialed in on bias and offset. I'm damn tired of working on it. Service manual errors make working on stuff much less fun than it should be, following the manual to only do something that is away from the proper adjustment or worse damages the unit. But as folks say it is part of the landscape of working on this gear.

Anyway, we are getting there. Letting it warm up to normal quiescent operating temps going to do the final bias and offset dance and put the covers on it and have it get picked up. Probably have to listen to it first cause my friend might not be here for a few days.
 
Service manual errors make working on stuff much less fun than it should be
You mean like this?
uel2mzd.jpg

Honestly, I don't remember that issue. I just found this in my old google albums from years ago.
I must have made it for a reason. I'm pretty sure it's another orientation error though.

Did you modify the tuner PS like this?

QXEMmCo.jpg


It's a pretty common mod.
 
Not quite. Since this was a budget repair, he doesn't want to spend money I got a pair of 300Ω ceramic wirewound and cut some slots in that wall and used wire ties to hold em in place. Same two resistor configuration as original. Coulda gone 1 resistor and that fancy metal one, chassis mount and mount it to the chassis but that would have been a buck more. Some people. I just don't understand it.

That error in the manual wasn't even an issue as I recapped without looking at it. Replaced like with like in same orientation.

I don't know what was causing the issue of the heat. Might be just lack of use. This unit was new to Spiney and he just wants to hear it and see what he thinks. He has an Onkyo TX-904 that handles his needs but this should be better and might make it out of the closet the Oink lives in.
 
The issue that got me is the bias and offset crap in the manual. So much easier to use an emitter resistor and do the bias that way it is straightforward what VRs to use. The manual has it wrong and the mA instead of a fuse is just asking for trouble with a digital meter. Pops the fuse. A simple adjustment of the leads one of the emitter resistors per channel makes em easy to grab and my grabbers come off and I leave em in place while I move the meter to the leads plugged into a speaker connection for offset. I know this receiver way more than I wanted to.
 
I don't know... The emitter resistors are kinda squeezed in a crammed spot and a slip of the probe isn't too improbable.
I use a spent fuse tool to take current measurements in series on the fuse holders. It's basically a spent fuse with wires soldered to
it's end that go to the meter. The bias routine goes like this, and it's pretty straight forward once you realize you need to take the SM
with a grain of salt:

---------Left Channel--------------------Right Channel------
------bias-------------DC--------------DC------------ bias------
(-) VR03 (+) | (+) VR01 (-) | (-) VR02 (+) | (+) VR04 (-)
--------------F05-------------------------------- F04---------------
 
without the bracket that holds 2624 in place, plenty of room and so much easier. And when you do that you don't need to look at anything. Left is left all the way across. The manual shows the Left channel fuse and oh the heck with the manual it is wrong.

Thing is in the case now and may get hooked up tomorrow, just to see what it will do but I'm enjoying some speakers I haven't used in a while with the sub I haven't used with them before on the main rig. And the sound room is clean and orderly (as best I can) right now. Not many extra wires going everywhere.
 
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