Wednesday, February 3, 2016

Harman Kardon 430 Dual Power Receiver

Harman Kardon 430 Dual Power Receiver 

Thought I’d do a quick write up on a nice H&K 430 dual powered receiver we received in recently. 
Very similar to the 330 and 730 topographies, the 430 is rated at a minimal 25W/ch, the biggest retraction from the 730 is the lack of pre-out/main in jumpers. 

Power Supply & Dual Rectifications
The integrated separated power supplies is a neat feature of this H&K series. Quite a bit different than most supplies, the only issue Ive noted is one transformer is delivering a current draw of 1.25A for the bulbs running it a little hotter than the other.  Each rectification PCB A & B had the large electrolytic replaced with 330<MFD low impedance, high temp (105C) Nichicon PW’s along with the SIB01-02 updated to a ultra fast diode and 1/25V/1/13V diodes updates. 

Driver PCB
The symmetric driver pcbs has a mounted heatsink to the PCB hosting the TO-3 output device bank, new MICA and compound was applied here along with pin junctions reflowed. The original 2W emitter resistors were replaced with .47 5W wire wounds for better dissipation and pigtailed for future bias adjustments. New precision Bourns bias potentiometers were installed, notate the common wiper configuration. 1st order differential pair transistors were replaced with HFe matched 1845 BJ-transistors along with Q421/422 which is a failure prone 2c458 TO-92 BJ-Transistors, these are commonly found in the RIAA stage of Marantz and in pre-amp stages for low signal gain drivers, very problematic and noise prone. Electrolytic were replaced with low impedance, high reliability Nichicon PW and .22/250V film updates to a polypropylene type.  D407/408 diodes were updated to ultra fast 4005 type.

Bias Notizen
Links und Recht beim emitterwiderstand R430 und R429 beim VR402/1 fur 25mV

All the electrolytic within the RIAA and tone stages were replaced with low impedance, high reliability Nichicon PW and audio grade Elna Silmic II, the RIAA stage small MFD capacitors were replaced with high quality WIMA polypropylene type film capacitors with a 2mm footprint. The Tone control can be tricky to get at, make sure you pull the PCB from the chassis as this is the best angle to clean all the potentiometers and switching controls. Updated from the early H&K receivers the 2SC1344 PNP BJ-transistor was used exclusively vs the 458BJT. 

RF Stages

Like many RF stages we do, all the tantalums were removed and replaced along with electrolytic dielectric capacitors to Nichicon PW low impedance capacitors.  Special care was taken to clean the shaft and tuning capacitors along with a new replaced stereo indicator. 

No comments:

Post a Comment