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Help--Need a Harman Kardon 430 tech.


JohnW

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13 minutes ago, JohnW said:

When testing resistance of the cap, what should I set my Multimeter to?

 

200k should be good.

 

As for capacitors when you pull the old ones off measure the lead spacing on the board and also the casing diameter. Caps have gotten smaller and the 2200uF 35v that I linked below has a 7.5mm lead spacing. Case diameter is most likely not going to be an issue since caps have become smaller but using too small lead spacing makes the capacitor sit weird on the board so you should try and get a capacitor with the correct lead spacing. Digikey is nice because you can use the lead spacing as a search criteria along with voltage rating and capacitance and view the results.

 

https://www.digikey.com/en/products/detail/rubycon/35ZLH2200MEFC16X25/3564493

 

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4 minutes ago, JohnW said:

Will do, thanks. 
 

C4 kept going to infinity.

 

That's typically a good sign but not a definitive test.

 

The only way to really measure leakage current is while you have the cap out of circuit hook it up to a DC supply and set your meter to read DC current and place the meter in series with the capacitor. You can even use a 9v battery to do this test, it will draw a lot of current while charging up but once it reaches maximum voltage watch the current meter to see how much leakage current is passing through the capacitor.

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There are a number of good threads on the 430 at Audiokarma regarding a recap.  I didn't worry about size for the power supply filter caps when I did mine a few months ago and just used heat shrink tubing to protect the leads.  Also, the original power supply filter caps have four soldered legs - two dead legs for stability and two live legs, you can figure out the (+) and the (-) off the lettering of the original caps.

 

Audiokarma Links: https://audiokarma.org/forums/index.php?threads/dlucys-guide-to-harman-kardon-twin-powered-series-430-630-730-and-930.960074/

 

Also, be careful when working on the preamp board - while the main amp board is NOT mirrored about a common axis (my initial downfall, swapping the +B and -B when rewiring one channel, blowing a diode, only took about four hours to figure that one out), the preamp board is mirrored - so watch the orientation of capacitors and transistors.  Also note that the parts list in the tech manual and the PCB call out C407 and C408 as 470uF / 16V; the circuit diagram in the same manual shows 1000uF / 16V; but the installed part is 1000uF / 25V.

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1 minute ago, JohnW said:

Sorry, Bill--yes, I checked D5, D6, D7, and D8. All were functioning. 

Yes, my mentioned about a relay switch also. It is the click that is typically heard seconds after turning on a unit.

Guess you are looking to replace suspect cap(s) now. 

A couple of Youtube on the 430s interesting. Following here...

 

 

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47 minutes ago, billybob said:

Yes, my mentioned about a relay switch also. It is the click that is typically heard seconds after turning on a unit.

Guess you are looking to replace suspect cap(s) now. 

A couple of Youtube on the 430s interesting. Following here...

 

 

Unless I'm mistaken (and I very well could be, I am obviously a novice here), I don't believe it has a relay when you power it up...at least I don't hear one when it starts...is there one in the schematics? I believe I read that there isn't one as well. Because if that's the case...not having one might be the source of our initial overload issues. 

 

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29 minutes ago, billybob said:

Yes, my mentioned about a relay switch also. It is the click that is typically heard seconds after turning on a unit.

Guess you are looking to replace suspect cap(s) now. 

A couple of Youtube on the 430s interesting. Following here...

 

 

The 430 does not have a speaker relay however there is a slow start circuit on each channel in the the power amp.

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23 minutes ago, BadChile said:

The 430 does not have a speaker relay however there is a slow start circuit on each channel in the the power amp.

 

Yes no speaker relay just 3A fuses for speaker protection.

 

Where is the slow start circuit for each channel? The pass transistor for each rectifier board 'A' and 'B' have two different time constants, 'A' being around 2 seconds and 'B' is 4 seconds. The output devices from rectifier board 'C' gets their power immediately. Board A is regulated 13v and board B is regulated 24v.

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4 minutes ago, captainbeefheart said:

 

Yes no speaker relay just 3A fuses for speaker protection.

 

Where is the slow start circuit for each channel? The pass transistor for each rectifier board 'A' and 'B' have two different time constants, 'A' being around 2 seconds and 'B' is 4 seconds. The output devices from rectifier board 'C' gets their power immediately.

I believe (based on other sources) that it is on the Main Amp board (C405 and C406), not on any of the A/B/C boards.  But I'll defer to others to correct me if I'm wrong.

 

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12 minutes ago, BadChile said:

I believe (based on other sources) that it is on the Main Amp board (C405 and C406), not on any of the A/B/C boards.  But I'll defer to others to correct me if I'm wrong.

 

From the rectifier board C the outputs B+/- go via wire to the main board connecting to V+/- where you can follow the board traces all the way to the output devices Collector/Emitter. They should get power almost immediately. The other sections fed from board A 13v, and board B 24v will have a 2 and 4 second delay from the base RC time constant.

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3 hours ago, billybob said:

Yes, my mentioned about a relay switch also. It is the click that is typically heard seconds after turning on a unit.

Guess you are looking to replace suspect cap(s) now. 

A couple of Youtube on the 430s interesting. Following here...

 

 

If you have links, that would be great...so far all I can find is sales demos and Rosie O'Kelly...which I haven't found particularly helpful. 

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On 2/15/2022 at 12:54 PM, BadChile said:

The 430 does not have a speaker relay however there is a slow start circuit on each channel in the the power amp.

BadChile, any idea why it would start with 5-6 volts on the R9 resistor before it drops down to .7-.8? That's the only problem with this amp. 

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