DCC Voltage low

[paradisecs]

I have a DCC 1  Code C with 311125-D in it.  I tested the voltages (while still in SPS160).  The -27 voltage tests out at -13 and the -13 voltage reads at -10. All other + voltages read within specs.  So I went ahead and recapped all the lytics as well as  replaced q3100, the old one failed a diode test.  I'm still getting the same voltage readings. 

I've read through Tony's Black Box book and I don't see anything saying what could cause the -27 to be that low.

Ron, in the Troubleshooting guide, Phono Procedure #2, you say that if the -27 & -13 voltages check back to locate problem in DCC power board or cabinet wiring.  I have replaced the the lyctics and replaced the cr3102/3,8/9 with new 1N4002, new R3100 and R3108, as well as a new Q3100.   Is it possible I have a bad cap still, maybe c3108 if I'm reading the schematics correctly?  Or could the transformer be bad?  What in the cabinet wiring could cause this?

Stephen

[Ron Rich]

Stephen,
Are you "bench checking" this unit--If a DCC-4 is the "income Totilizer" plug jumped at the large outboard neg. transistor ? ( I would not use 1N4002's--I would at least go to 004's). What is the voltage reading on the neg. fuse ??
Ron Rich

[paradisecs]

Ron,

DCC1-C. My bench testing is a spare STD160, so the readings are when fully hooked up. Why the upgrade from 1N4002? I'm going to check voltages at the components today so I'll check the fuse voltages and let you know.

Stephen

[Ron Rich]

Hi Stephen,
ALWAYS check on "the bench"--or at least remove the plugs for the Gray/black boxes, as if one of them is "shorted" it will lower that voltage. Safety on the diodes--the transformer is not adequately fused(IMHO), and shorted diodes will blow the transformer. Ron Rich

[paradisecs]

Okay, found that my new R3111 was not doing 5.6 Ohms but somewhere around 60k, so that was a bad resistor.  I'll go back and check the resistors in circuit just to make sure there isn't another failed one.

TB3107 & TB3106 voltages are now -41 & -31, respectively.

Voltages at the F3102 is -42.3 and F3101 is 41.5.

I checked Q3113 for voltages and across all three points I'm getting -41.1.  If I'm reading the schematics correctly it should be -42 on the Collector (measured on the case?), -27 on the Base, and I assume -27 on the Emitter.  That is assuming I'm checking things correctly.  

I've checked various other points for voltages against Tony Millers schematics with the voltage tests on them and I get wrong readings throughout the circuit.  I assume that if one component goes haywire then it would be off from that point on.  I'm just not sure what or where the root of the problem is yet.  

Stephen

[Ron Rich]

Stephen,
What do the -13 and -27 test points read ? Are you reading these voltages without the black/gray boxes plugged in ?? Is the IT plug jumped, or not ? ?? Ron Rich

[paradisecs]

Yes, I have the IT jumped. The voltage at -27 test point is -41. The -13 test point is -31. As you recommended I have it on my bench, not fully installed in a phonograph.

Stephen

[Ron Rich]

Stephen,
Look at the 13 volt ZD, and the small signal diode next to it- the -13 MUST be correct--first-replace them both--also replace the TO-39 transistor. Check all resistors in the circuit-- Ron Rich

[paradisecs]

Those would be CR10 & CR12 and Q3120, correct?

Stephen

[Ron Rich]

Stephen.
Going by my great, but not too long memory--yes-- I don't have a schematic here--
Ron Rich

[paradisecs]

Thanks Ron, I thought I had it correct but confirmation is great.

As I looked up part #s I came across something else I hope you can shed light on. In the Electronic Parts Catalog Ver 3 it lists CR-3133 as Seeburg #62-309703 Sil Switching Diode 75V; which is a 1N4148 in Tony's Black & Gray book cross-reference. But his book then lists that diode as #309384; which is a 1N4817 or 1N4818. So what is the correct replacement to use?

Stephen

[Ron Rich]

Stephen,
Any diode can be used anywhere a "switching diode" is called for in Seeburg products.
Ron Rich