Two Kenwood KR-5600s in the house, need help on one

OK. New readings with just the two power wires hooked up. Pin11 5.0, Pin 5 40.0, Pin 15 40.0, Pin 16 5.0, Pin 3 21.4, Pin 4 -21.2, Pin 12 +39.8, Pin 13 -39.8

R1 40 27, R3 24 .3, R2 -39.8 -21.3, R4 -21.4 -.3

Pin 5 and Pin 15 are now a concern. Pin 15 is supposed to be a ground. Perhaps those two white wires that I left off are how it grounds. Not sure if wire color coding in receivers is the same as industrial control circuits and house wiring.
 
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Pin 5 and Pin 15 are now a concern. Pin 15 is supposed to be a ground. Perhaps those two white wires that I left off are how it grounds. Not sure if wire color coding in receivers is the same as industrial control circuits and house wiring.
Grounds are most likely black, maybe green, almost never white. You need ground at 15 or the regulator circuit (going out pin 5) won't regulate, and float up to the supply voltage. Look at your other unit for reference....My 2 cents.
 
Thanks. That is what I was thinking. I will look at my reference receiver prior to putting the rest of the wires back on. There is no guarantee that the wires were put back on the correct pins prior to me getting it. I used tags to number all of them, so they were put back as I found them. Tomorrow I should know if the voltage will regulate, then it is on to find why wire #31 is wreaking havoc.
 
I can guaranty that the wire colors are completely random. White is not necessarily neutral, green is not ground, yellow is not a separate source, blue and brown are not necessarily DC, and orange is not necessarily a phase. I cut my teeth on industrial control, and NEMA was the governing code in machine tools and equipment. This stuff is even worse than IEC, marine, and aeromotive. I believe the color is like barn paint, and thus is dictated by what was least expensive that day. You really need to put on dark glasses and follow the diagrams.

As for your power supply measurements:

Pin 3, 21.4
Pin 4, -21.2
Pin 5, 40.0
Pin 11, 5.0
Pin 12, +39.8
Pin 13, -39.8
Pin 15, 40.0
Pin 16, 5.0

R1, 40 27
R2, -39.8 -21.3
R3, 24 .3
R4, -21.4 -.3

As sregor stated, Pin 15 needs to be wired to a chassis ground, whatever color wire you use. That might put Pin 5 back into a ground reference and regulating properly.

Similarly, the voltage drops across the resistors will not be correct until Pin 7 is connected to a chassis ground. You might as well ground Pin 6 at the same time to pull the filter capacitors back into a reference.
 
Yes sir Watthour, That is my plan. I will trace wires as well since insulation color is not reliable. I think plugs and wiring harnesses were around when these receivers were built. Labor must have been cheap.
 
I traced all of the wires today and even took a look at the working receiver. All looks good as far as where the wires were connected. I left wire number 31 off for now as I know that it is creating a voltage drain. When I turned it on and checked voltages again, I found that there is only a fraction of a volt on the base of the transistor. Plenty of voltage waiting to be let through, but it isn't going to happen until I find what is blocking the flow to the base. If I did my math correctly, working from the 38 volt source and through the three resistors between the source and the transistor base, there would only be maybe half a volt left. So, my novice thinking is the capacitors must not be passing current. I didn't have time to take the board back out today. When I do, I will pull the two caps and check them.
 
You have 0 volts (gd) at pin15? If so, the Zener is probably shorted - dk5 - wz 140. Standard 14 volt Zener - 1/2 watt (there is a suitable 1nxxxx sub, and a few other crosses, but not handy to me right now.)
 
Steve, pin 15 is a ground. I'm trying to get enough voltage at pin 5 to drive the tuner. The output side of R6, which is the base leg of the transistor, should be 14 volts and it is less than one volt. I think if I can get that voltage right, the transistor will start passing current through to pin 5.
 
Steve, pin 15 is a ground. I'm trying to get enough voltage at pin 5 to drive the tuner. The output side of R6, which is the base leg of the transistor, should be 14 volts and it is less than one volt. I think if I can get that voltage right, the transistor will start passing current through to pin 5.
As I said - probably bad Zener diode...The only other thing I can think of is that the transistor itself is bad, i.e. it is acting like a diode and not supplying current, but that isn't that likely.
 
Just for the sake of argument, and after looking again at your earlier photo, have the overheated traces and the associated solder joints on the PS board been cleaned up and resoldered to assure proper connections?

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Some of those power resistor solder joints appear to be tarnished, and possibly open. If any of R5/R6/R9 are disconnected, voltage at the base of Q1 will be affected. Check that D5 and C14 are also intact.
 
I cleaned up the board and resoldered anything that looked suspect the day before yesterday. Also used the ohm meter to check conductivity on all traces.
As I have said before, I'm trying to catch up with the theory of how all this stuff works. I'm not trying to be or to sound argumentative and I apologize if I do. What I am not understanding is exactly what path the current flows to get to the base of the transistor. My assumption has been through the resistors. I would really appreciate it if someone could describe the current flow from say R5 to the base of the transistor.

Voltage readings are: R9 in 39.8V out38.4V, R5 in 38.4V out 19.6V, R6 in 19.6V out 0.8V. The zenor has 0.8V on one side and 0 on the other.
 
Your assumption about the current source for Q1 regulator is correct. The +38V supply from the main transformer and bridge rectifier should always be present at the main filter capacitor, C5, which is also Pin 12. Your earlier voltage measurements indicated that there was +39.2V present there - Close enough.

R9 (56Ω / 1W) should drop that to around 34-36V (guesstimate) when there is some load on the circuit, thus presenting that voltage at the collector of Q1. R5 and R6 in series present a total 1,640Ω resistance before the connection to the 14V zener. This zener should shunt any voltage above its bias point through the device to ground through the choke, L1. Your measurement of 0V on the lower end of the zener verifies that.

NOTE: L1 will present almost no DC resistance and is likely there only to suppress any AC noise left in the power supply after the main rectifier and big filter capacitor and any ringing in the regulator transistor.

The zener (D5) should stop current flow at voltages below 14V, thereby regulating that point of the circuit at 14.0V. Since there is only 0.8V measured at the top end of D5 and 0V on the other end of the zener, either the zener itself is shorted, or one of the parallel capacitors, C10 and C14, is shorted. sregor suggested a shorted zener earlier, and that may prove correct.

When there is 14V present at the zener, it is also at the base of Q1. Presuming the typical 0.5 to 0.6 V forward drop of the junction (in any silicon bipolar device) the resultant voltage at the emitter should be held to 13.5V.
 
Thanks Watthour and sregor. My brain is a little dense but it will still absorb information and the light is beginning to turn on, albeit dimly. I'll try to find some study material on regulated circuits. I understand how the zenor can regulate voltage but need to tie in just what the capacitors do in a situation such as this. I know that they are used to "smooth out" the output of a bridge rectifier so I'm thinking that they basically do the same here, keeping the charge at a constant 14 volts so that the transistor doesn't flutter, for lack of a better term. I've started shopping for components using the filter on Mouser. It made me quickly realize that I had better back up and learn all the variables in resisters and capacitors for starters. I was able to find the resistors, but quickly got lost looking at capacitors.
 
You're right about the capacitors filtering, and in the case of the regulator transistor the extra caps are there to probably "dumb down" the circuit a little so that the transistor and zener don't constantly swing back and forth with the smallest of voltage ripples (ringing), instead absorbing some of the highs and lows to make life easier for the transistor. If the tuner circuit sees 13.45 to 13.55V it probably won't care, even a little.

In a power supply circuit such as this, operating at relatively low frequencies, a plain, old electrolytic with an appropriate capacitance and sufficient voltage rating for the circuit (plus a bit of safety factor for voltage) will be just fine. The rest of the details are the temperature rating and trying to get the lead spacing reasonably close to what is there or what you can work with. Capacitors rated at 85°C should be good for this circuit, and since most electrolytics are a lot smaller (physically) than they were in the 1970s-80s, getting one to fit is rarely a problem.

Out of curiosity, did the zener or either of those capacitors show a short in a resistance check?
 
I haven't pulled any of the capacitors or the zenor out of the circuit to do a decent test. I did an ohm check across the zenor with it installed and there was no conductivity in either direction.

Is it a good idea to go ahead and replace all of the capacitors on this board? I sort of hate to just order $2.50 worth of stuff and have to pay $6 or whatever for shipping.
 
It would be best to test out of circuit.

I hate to spend your cash, but it might be reasonable to also get a replacement for Q1, just in case. A MJE15030G would do it, for about $1.50. A couple of spare fuses and possibly even a dial lamp or few ( )could build up the order to ease the pain of the shipping.
 
I was actually considering buying all the caps. If I get deeper into this one and can't make it work, I can always use them in the other receiver.
 
Oh, and thanks for the number. I've been trying to find threads that have that sort of information in them but not too much has been posted about KR-5600s
 
but it might be reasonable to also get a replacement for Q1


X2. I've seen more than a couple 2sc1419s fail. 1n5244B for the 14v zener. These guys are offering free shipping - I have not used them yet, but plan to for my next order.
 
Thanks. Free shipping and a new customer discount as well! Are there any brands to avoid on capacitors? I don't want to go to the work just to be installing junk parts.
 
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