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Need help with Kenwood KR-4200

Two KSD1616 transistors are in the mail heading your way.

They are both hfe 190 which is near the high end of the range in the original part's specification (a good thing). The original part's max rated power dissipation is .4w and max collector current is .5a. The max ratings for KSD1616 on these parameters is .75w and 1a. So it is a more robust part.

There may be a little scotch tape residue on the legs. That should be cleaned off with some alcohol before soldering.

Also...just checking...if you have not soldered transistors before you should be aware that they can be damaged by too much soldering iron heat. It is best to have everything absolutely clean and have a hot enough iron so that time with heat applied to the joint is minimized to the greatest extent possible. It is not the same as soldering caps or resistors.

If it was me I would probably also replace that cap again too, if I had a fresh one sitting around.

Good luck, hope this does the trick for you.
 
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Excellent and thanks for the tips! I've never soldered transistors so hopefully I don't muck things up too bad lol.

I'll let you know how it goes and thanks again!
 
Parts showed up in the mail today. Gotta love speedy shipping from the US :)

Before I begin soldering, do the new transistors have the same pin layout at the old?
 
Yes they have the same pin out: ECB

For future reference you can get spec sheets for currently available transistors (or anything else) from Mouser or Digikey on the product's page. Spec sheets for NLA parts can usually be found here: http://www.datasheetarchive.com/
 
Hummmm..

So I replaced Qe 20 with the new transistor and now the relay will not even click on. I put the old one back in and it is working as before. Any ideas?
 
Does the original 2sc1213A have the same physical shape as the ksd1616A?

Some older small transistors have a rectangular body with a beveled top instead of a rounded body with one flat face.
 
OK, those being different shapes might possibly cause confusion as to which pins are which. Having incorrect pin-out could explain why the circuit doesn't function with the new transistor in place.

Both have E-C-B pin-outs left-to-right. On the KSD1616A the flat face would be facing you to make the E-C-B correct. On the 2sc1213A the side with the beveled top should be facing you to make E-C-B correct.

I just looked at the 2sc1213A that I removed from my KA-7100. On it the marking that reads "C1213" is on the back of the transistor. When that side is facing you the pin-out would be reversed.

If one of the new KSD1616A's was installed into the circuit I do not know whether any damage to the transistor could have occurred. Does your meter have a diode testing function?
 
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Beautiful! I'll put it in the correct way tomorrow and see how it works. Even if I did damage it by putting it in backwards, you sent me two so we still should be able to get this old girl up and running. :thmbsp:
 
Late to the party... First a tip. Your meter is your friend. The collectors of both those transistors is the center lead, and the diode test on the meter will point you to the base. I always check this, as it takes a few seconds, and eliminates having to look up and interpret spec sheets, especially if there are errors.

Next - some trouble shooting queries. First, make sure the supply voltages are right. Check on the power supply board where the diodes dk2 and dk3 connect to rk9 (220 ohms) and ck5 (10 uF) This voltage should be in the low 40's. If it is too low cap ck5 could be bad. Next, check voltages around qe20 (relay drive transistor.) Looks like it should be about 2.5 to 3 volts on the base. If this is not there, then check the voltages on the transistors coming in. There is a misprint in the schematic. The base of qe18 and collector of qe17 should be 29 volts, not zero.
If you are getting voltage on the base on of qe20, but the relay is not pulling in, you also want to check the resistors re56 (680 ohm) and re55 (100 ohm), and the circuit tracks between them. Also the 220 ohm resistor on the power supply board. The relay drive current goes through all of these, and if any are off value, will cause problems. Good luck
 
The 2sc1213A relay driver that I pulled out of my KA-7100 had hfe of 33. It started life in the 100-200 range. This is a known and common issue. When the hfe (gain) gets too low the transistor is no longer strong enough to hold the relay open.

cptnCanada please go ahead and install, in correct orientation, the new transistor that I sent you and see if that resolves the issue.
 
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So no luck with changing Qe20. The relay is still triggering although it seems not as often.

I took the time to measure values suggested by sregor and it appears to me something is amiss with Qe17.

Main supply voltage is 48V

Qe20 values are 2.3,2.3,2.9
Qe19 values are 2.3, 26.3, 1.1
Q18 values are 28.9, 1.1, 28.9
Q17 - This is the aluminum can transistor that is not like the rest in the circuit and is not what the SM specifies. It is a 2sc1416 metal can type. I can ony read one pin as 28.8, another as 0.0 and the other trips the relay every time I hook up the DVM.

Resistors test in spec.

Do you guys thing there is something wrong with Qe17? Roger, could I sub in one of the transistors you supplied for Qe17. The SM specifies a 2sc1213a there.
 
I was lucky enough to catch a reading of the collector of Qe20 when the relay tripped....50V! hope I am not damaging things by letting this happen.
 
50v with relay off is probably fine. The off voltage (to me) would be the 1.1 on the collector of Qe18. I would expect it to be zero. Suspects would be leakage through qe18 or ce21 or qe19. (yeah, ce21 was changed previously.... )

Qe17 is probably ok, as base and emitter of qe18 are the same, meaning it should be in the off state and is what you want for relay operation.
 
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cptnCanada said:
So no luck with changing Qe20. The relay is still triggering although it seems not as often.

....
Click to expand...

I would have liked to see how things work with both a fresh Qe20 and a new Ce21 at the same time. You did install a new Ce21 only, and reported it fixed. But then the intermittent issues came back. So I don't know whether it is possible that running a new Ce21 with a compromised (original) Qe20 might have stressed the new Ce21. Maybe not, but I just don't know.

As I do not have sregor's knowledge of circuits, combined with the fact that he currently lists a small number of relay circuit components as suspects, at this point what I would probably do (not suggesting that you do this) would be to shotgun those components that sregor mentions in his most recent post as well as a new Ce21. Then, even if the issue was not resolved at least some possibilities would be eliminated.

Bear in mind that we are still talking only about components of the relay circuit, and the suggestions I made earlier were based on (what I believed were) the key components in the relay circuitry. It is also possible that an external fault could be causing the relay to open. After all, it is the job of the relay circuitry to open the relay to protect the speakers whenever certain fault conditions are detected.

I do not have enough knowledge about circuit operation to be able to give you guidance. You are a smart guy and with sregor's assistance I am sure you will get it done. Looks like it will be a bit more of a learning curve than had been anticipated, and you may possibly need to order some parts.

FYI, I noticed on your schematic that Qe18 is also not a 2sc1213A, I missed that before. And it is on sregor's suspect list.

Good luck. I will keep watching. I am curious to see how this gets resolved. If if see a spot where I can add anything useful I will do so. :yes:
 
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I removed all the transistors in the circuit to test on my DVM in diode mode. They all seemed ok so me thinks its shotgun time.

I've never ordered transistors before so how do these equivalents sound:

Qe15-17 Schematic calls for 2sc1213a so I will get more KSD1616a *see note below about Qe17.

Qe18 Schematic calls for 2sa673a. My google found NTE290a as an equivalent.

Qe19-20 Schematic calls for 2SA1213A (b or c). I have the two transistors you sent me Roger installed in these spots.

*Although schematic calls for Qe17 to be 2SC1213a, the board has a 2SC1416 installed and it looks factory installed. Google turned up NTE123a as an equivalent for this.

Do these replacements sound good?

I will also get a proper replacement for Ce21.

I know this receiver in by no means totl, or valuable for that matter. I just can't seem to find a reason to give up on it. Worthwhile or not, I think it deserves to be saved and enjoyed for the next 40 years. Hopefully this shotgun will solve the issue once and for all. Then it will be on to new caps :)
 
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