Harman Kardon 330 B troubleshooting

[dlucy]

One question, i find the following part on mouser, that must be an equivalent to the KSC1845F ?

search KSC1845F =
http://ca.mouser.com/_/?Keyword=KSC1845FTA

Yes, the following part, on the Canadian Mouser site, is the right substitute or modern replacement for a 2SC458

http://ca.mouser.com/ProductDetail/ON-Semiconductor-Fairchild/KSC1845FTA/

The KSC1845 is the Fairchild model number, the F is the hfe or gain code, and the TA means the parts are delivered on a roll of tape instead of in bulk. It's the only way Mouser sells them (and it is fine).

One thing to remember is to look at the quantity discounts. In the US right now the KSC1845F is $0.21 USD each when bought in quantities less than 10. If you buy at least 10, that price drops to $0.14 and when you buy at least 100 it drops to $0.06. So, for these common-in-your-330B you may want to buy 20 or 30 so you've got enough to replace all of them in the unit plus a few extras for mistakes.

 

[Jpkwd]

still checking where i can order parts : mouser is charging 20$cAD for shipping which raises the price of the fix to a whole new level
Will be looking locally to see if i can find the parts

so cheapnis is the name of the game until i get new parts i'm guessing.
SO, to trouble shoot the issue and based on the rightful conclusion from Doug, i studied the schema of the amp and came up with the conclusion that Q502 and Q504 were dedicated to the left channel

So if Q502 is dying (channel volume difference) and Q504 is strong, i thought i could simply swap them to see if that swapped the issue form Tape amp to Tone Amp.

So i am now quite surprised (it's my first soldering of transistors and troubleshooting of that sort) : my swapped kind of worked ...

Kind of, you know, fixing one issue always brings attention to other issues.
Now, The channel volume difference disappeared
unfortunately the "dark side of the moon explosions" kind of static or popcorn sound came back on the left channel. Rather loud after 20 minutes of playing music, still in the left channel.

So i am wondering why the channel difference disappeared all of a sudden
there is something else going one..not sure what
Perhaps capacitors or other transistors... not sure how to troubleshoot this one


by the way, went through testing with DMM of the transistor, both 502 and 504 appeared ok, same reading on both are .693mv in diode testing

 

[Jpkwd]

hummm, disabled speaker switch, raised volume to max, wait a couple of seconds, say 30 seconds,
flipped the speaker switch back on, ....no more static....

i think i got it. at least for now, its working ok.

lets see. will close the receiver and wait. then clean, and check again : Like Captouch was pointing out there might still be some crap in the controls.
that thing is almost 50 years old so it might very well be plausible

will revert back with more info

 

[Jpkwd]

ok so an hour later, third cleaning, its all good now, no popcorn sounds or explosion in the left channel.
i think it,s fixed
not perfect ( i aint perfect either)

but its working good... i fixed it ? unless otherwise noted, i think i did with fantastic help from you Doug and captouch!

remaining is the resistors on the rectifier boards to change and the weird resistance and bypass of the ac fuse...

i cant get over how clean the 330 preamp and amp boards were on DOugs picture so i am listening to music right now with my newly functioning 330B and thinking i will changed these transistors and recap that thing if in the long run i like it as much as i expected i would

for now, i'm a quite the happy camper !

 

[Jpkwd]

doug, would you do me a favor ?
If you have a 330 (B would be even better) lying around, or perhaps a picture you took earlier when you were repairing one, would you take a picture of the AC fuse underneath where the outlet is? Id like to see an unaltered AC fuse circuit

if you look at the previous picture i posted, you'll see that there has been some tampering with the ac fuse of my 330.
I got the amp opened with guts exposed, and touching the frame, i'm sensing some small electrical shocks !
not good, this needs to be fixed

 

[Jpkwd]

this is what i need to fix

 

[Jpkwd]

Some updates on the project

A) i got the shock from the frame issue resolved (frame and volume+Balance knobs would give small shocks). That appeared to be linked to the "Death Cap" per other threads (i learn new tricks everyday).
Third picture in my previous post, i changed the 0.01 capacitor (C7) and had to flip the plug for the voltage to drop on the frame and pots. No more shocks. that's good news

B) the fuse that is bypassed (wires cut Fu1 fuse holder) in the 3 photos i posted in my previous posting appears to be replaced by 2 new fuses (2A) in the receiver. They are not Fu2 and Fu3 near the amps.
i am starting to think this is a tweak that is correct. not completely sure, any feedback welcome here.

C) A resistor is missing R5. It seems that in the RV schematics, there is no capacitor (0.01, C7) but rather a resistor only 2.2M 1/2watt connected to frame.
In the MV schematics, both a resistor (R5) and a capacitor (C7) are connected to frame. I can't find R5 in my 330b. Like pointed out in B, changing R7 fixed the ac "leakage" issue.
I'm confused here. Not sure why there are two variants RV and MV and why the added fuses were introduced in my receiver or why the R5 resistor is missing.

Any advise welcome

 

[Jpkwd]

A great thank you to you Dlucy for the guidance in fixing the receiver.
It's now a fully functioning receiver.

Thank you also Captouch for reminding me about cleaning the pots thoroughly.

In short,
A) Replacement of death capacity still works flawlessly.
B) Circuit protected with two fuses instead of only one
C) Mystery solved.I found the resistor in a sleeve on the ac plug connection.

Only little problem now is that the transformer hums a little more than i would like it to.
So i'll see if any mechanical fixes can solve this issue. if not, that will be a new part.

So thanks again, all the help was very very appreciated.
I am enjoying this new hobby more than ever.

no i'm back to my initial project, trying to fix the Yamaha CR-1040. that is still a challenge for me.

 

[captouch]

Glad to hear you're mostly sorted out.

It just hums mechanically, not audible through speakers? And you've tightened it down so it's not loose?

I wonder whether some rubber spacers between the transformer and the chassis can also help absorb some of that vibration. Seems a shame to spend the $ to replace it if it's just physical vibration that might be dampened in another way.

 

[Johnno_Oz]

Doug is the MASTER on these, glad you've brought another back to life.

A 330b followed me home from the pawnshop one day and I was so glad these great little receivers had a caretaker.

 

[Jpkwd]

Glad to hear you're mostly sorted out.

It just hums mechanically, not audible through speakers? And you've tightened it down so it's not loose?

I wonder whether some rubber spacers between the transformer and the chassis can also help absorb some of that vibration. Seems a shame to spend the $ to replace it if it's just physical vibration that might be dampened in another way.

Thanks Captouch,
Definitely mechanical humming: can't hear anything through either channel.
Another post here on AK identified the same issue with a 330B and pressing on the case would dampen the hum.

Loud enough to be heard standing in front of the receiver without music on and Can't really hear it with music on. The metal case is resonating and amplifying the vibration of the transformer (quite well i must say). Pressing a hand on the cover reduces to about half the noise and you can feel the transformer vibration.

As you suggested, i tried mechanical solutions :
- Tightened transformer covers screws
- added 2 rubber washers to each screws (probably 1/8th of an inch thick total) and grounded transfo with a wire to the case - i read this is a must since the rubber washers are remove the ground connection).
- Adjusted the screws holding the case of the receiver ( loosening one screw close to the face plate had some major effect)

Still can hear it but i would say it is down about half what it was before
Perhaps the next step will be to add shims made from paper or wood between the coils and iron core. Not completely sure that is a good idea.

 

[Jpkwd]

Doug is the MASTER on these, glad you've brought another back to life.

A 330b followed me home from the pawnshop one day and I was so glad these great little receivers had a caretaker.

Thanks Johnnz,
Doug definitely helped me a lot. All the detailed posts he created are very useful. Great little receiver this 330B.

 

[dlucy]

Thanks Captouch,Definitely mechanical humming: can't hear anything through either channel.
Another post here on AK identified the same issue with a 330B and pressing on the case would dampen the hum.

I haven't experience any mechanical hum from a 330 before, but I definitely understand how that would be annoying.

To help anyone who is pitching in with ideas, here are topside and bottom side photos of the power transformer in the 330B (this is the single-voltage version, not the multi-voltage version as that one has a big black cylindrical switch between the transformer and the tuner's variable capacitor box):



In that last picture, the bottom side one, you can tell where the power transformer is (on the other side) by located the two plastic-grommet-filled holes, the right and left side of the power transformer above it, where a pair of red wires comes through form the top through one and two green wires and one blue wire come through from the top through the other.

 

[wallsonic]

Hi. I know this is an old thread but thought I would drop this info in incase anyone is searching for transformer info. I used to work at a company that made custom coils and transformers.

The mechanical hum / vibration you hear is, as others have suggested, is most likely
loose laminations in the transformer core. Transformers are built of world and a stack of stain steel plates. After building they are dipped in either wax or lacquer to lock the laminations in place and eliminate hum. I suspect the lacquer is drying out and now the laminations are loose again.

Never tried it myself on a transformer but guitar pickup coils suffer a similar age related problem and can be repotted to eliminate the issue.

Really don't see why a trans couldn't have the end caps removed and drop it in a bucket of lacquer for a few hours. I do think I would let it dry for a week before reinstalling and powering it up tho !