Troubleshooting an old color organ circuit

Thread Starter

chuco61

Joined Jan 21, 2015
80
Do a diode test on the two pins, and note whether you get a reading with the red lead to the base, or with the red lead to the emitter.
Do another diode test between the base pin (from @bertus ‘s diagram) and the case. You should get reading one way round but not the other.
The repeat between emitter and case. You should get no reading either way round.
if the base-emitter reading is above 0.5 then it is probably a silicon Transistor, below 0.2 germanium.
Doing this gets me about .69 on two of the transistors, the other is .74
 

dl324

Joined Mar 30, 2015
14,332
Can you move any wires away from pads on the bottom of the board and take a higher resolution clearly focused picture?

1636654303579.png
Where does the trace circled on the left terminate? In the circled area on the right, are those two component leads?
 

dl324

Joined Mar 30, 2015
14,332
These are the component designators I assigned for future reference:
1636664497023.png
Note that there is an R4 and an R4A. I didn't notice that I had used R4 twice and didn't feel like feel like relabeling to keep them in sequence.

Could you use your meter to determine the polarity of the transistors? It looks like the small ones have their leads in a line. I'd start by assuming that the middle terminal was the base.

Also going to need you to give the pinout for the transformers.

Could you post the color codes on the resistors that are mounted upright?
 

dl324

Joined Mar 30, 2015
14,332
Here are some better images. I will get better readings on the transistors over the weekend.
Post the color codes on the resistors that are mounted standing up. Use the component designators I gave earlier.

For example: R2 = yellow-violet-??
 
Last edited:

bassbindevil

Joined Jan 23, 2014
378
If you're using that battery charger to power it (and not just to top up a battery), battery chargers don't deliver a constant voltage. It'll vary depending on the load, or what the brain inside thinks is appropriate. Have you measured what actual voltage it is supplying? Also, 1 amp capacity may not be enough to run 8 bulbs. 12V power bricks can be picked up cheaply at thrift stores and recycling places, if you don't have some lying around. (3.7 amp 12V Wii brick cost me a whole dollar.)
 

Thread Starter

chuco61

Joined Jan 21, 2015
80
If you're using that battery charger to power it (and not just to top up a battery), battery chargers don't deliver a constant voltage. It'll vary depending on the load, or what the brain inside thinks is appropriate. Have you measured what actual voltage it is supplying? Also, 1 amp capacity may not be enough to run 8 bulbs. 12V power bricks can be picked up cheaply at thrift stores and recycling places, if you don't have some lying around. (3.7 amp 12V Wii brick cost me a whole dollar.)
Interesting, thanks for this. I am using an automotive trickle charger 12v at 1amp. Maybe I'll charge a car battery and run it off of that. I have one laying around. The charger delivers 12v and I get 12v on the circuit as well. I have some bricks laying around, I'll find one with higher amps.
 

Thread Starter

chuco61

Joined Jan 21, 2015
80
Post the color codes on the resistors that are mounted standing up. Use the component designators I gave earlier.

For example: R2 = yellow-violet-??
R2 - Yellow Violet Black
R4A - Sliver Yellow Red Violet
R6 - Silver Yellow Green Brown
R8 - Silver Red Black Brown
R9 - Black gray Yellow Silver
R10 - Black Violet Yellow
 

dl324

Joined Mar 30, 2015
14,332
R2 - Yellow Violet Black
Also need the polarity for the transistors and the pinout for the transformers. If the transformers only have 4 pins, determining pins for windings will be straightforward.

Still need better pictures for the bottom. Wires that cover pads need to be moved so the pads are visible. Still need info on where the trace I circled near one end of the board terminates. It looks like it just stops.
 

dl324

Joined Mar 30, 2015
14,332
R4A - Sliver Yellow Red Violet
R6 - Silver Yellow Green Brown
R8 - Silver Red Black Brown
R9 - Black gray Yellow Silver
R10 - Black Violet Yellow
The color codes for R4A, and R9 don't make sense. R4A would be 720k, but that isn't valid value for a 10% tolerance resistor. R9 can't have a black band for the most significant digit.

Silver and black are never valid as a first digit, so the color codes for R4A, R6, R8, and R10 are backwards.
 

Thread Starter

chuco61

Joined Jan 21, 2015
80
The color codes for R4A, and R9 don't make sense. R4A would be 720k, but that isn't valid value for a 10% tolerance resistor. R9 can't have a black band for the most significant digit.

Silver and black are never valid as a first digit, so the color codes for R4A, R6, R8, and R10 are backwards.
Ah got it, I wasn't aware that the resistors were placed in a certain orientation, or maybe I just listed them wrong. I'll try again

r2 - yellow violet black
r4a - violet red (unless it is maroon?) yellow silver
r6 - brown green yellow silver
r8 - brown black red silver
r9 - brown gray yellow silver
r10 - yellow violet black

The transistors are style 1 from the previous post by Bertus.

Still trying to figure out the windings of the transformer.
 

Thread Starter

chuco61

Joined Jan 21, 2015
80
The color codes for R4A, and R9 don't make sense. R4A would be 720k, but that isn't valid value for a 10% tolerance resistor. R9 can't have a black band for the most significant digit.

Silver and black are never valid as a first digit, so the color codes for R4A, R6, R8, and R10 are backwards.
Ah got it, I wasn't aware that the resistors were placed in a certain orientation, or maybe I just listed them wrong. I'll try again

r2 - yellow violet black
r4a - violet red (unless it is maroon?) yellow silver
r6 - brown green yellow silver
r8 - brown black red silver
r9 - brown gray yellow silver
r10 - yellow violet black
Hello,

You might see that the pins of the transistor are not in the middle of it.
That way you can determine the Base and Emittor, the case is most times the Collector:
View attachment 252336
The transistor will likely have a style 1 connection.

Bertus
Thank you for this! It is indeed style 1
 

Thread Starter

chuco61

Joined Jan 21, 2015
80
Can you move any wires away from pads on the bottom of the board and take a higher resolution clearly focused picture?

View attachment 252448
Where does the trace circled on the left terminate? In the circled area on the right, are those two component leads?
the left one terminates into the black wire (ground), the right goes to R4 and C1 respectively.
 

dl324

Joined Mar 30, 2015
14,332
I wasn't aware that the resistors were placed in a certain orientation, or maybe I just listed them wrong. I'll try again
I didn't mean for you to post the correct order for the codes that were backwards. I meant to inform you that there is a correct order (but resistors aren't polarized). The tolerance, temperature coefficient, and fail rate bands, if they're present, are typically spaced away from the bands for resistor value.
The transistors are style 1 from the previous post by Bertus.
That still doesn't identify the polarity (NPN or PNP). There are what appears to be 3 other transistors that are in a black or brown package with their leads in a straight line.

You can determine transistor polarity with your DMM in diode check mode. If they're NPN, you'll read diodes with the positive lead on the base and the negative lead on emitter or collector. PNP would be the opposite; negative on the base and positive on emitter or collector.
Still trying to figure out the windings of the transformer.
Use your DMM to find which pins have a low resistance.
 

dl324

Joined Mar 30, 2015
14,332
the left one terminates into the black wire (ground),
I still don't see that. Could you take a higher resolution, clearly focused picture of that area?I rotated and mirrored the picture to make associating traces with components easier.
1637168273932.png
If they were connected, it could have been done in a better place. It looks like it just ends to me.

I wasn't aware that the resistors were placed in a certain orientation, or maybe I just listed them wrong
In your defense, the resistors were marked poorly.
1637168576139.png
The "gap" between orange and silver on R4 is barely discernable. On R3, there is no discernable gap; you just have to know that silver is never a valid first band.

EDIT: Just looked at some resistors I had on my bench and the "gap" isn't a sure thing. If you use resistors long enough, you become familiar with the standard values and use that familiarity to recognize the correct value.
 
Last edited:

MrChips

Joined Oct 2, 2009
25,931
From what I see,
R3 = 1kΩ 10%
R4 = 27kΩ 10%

Hopefully, when I have some time I will look at drawing out the circuit.
 

dl324

Joined Mar 30, 2015
14,332
From what I see,
R3 = 1kΩ 10%
R4 = 27kΩ 10%

Hopefully, when I have some time I will look at drawing out the circuit.
I was using those of examples of how to tell which end to read from. The only resistor value in question is R4A. Color code given was violet-red-yellow and that doesn't give a valid 10% (E12) value.

We still don't have transistor polarity. I'm waiting on that, the transformer pinouts, and clearer pictures of the bottom before investing more time.
 
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