Saturday, January 23, 2016

Kenwood-Trio KA-8300 Integrated Amplifier

Kenwood-Trio KA-8300 Integrated Amplifier 

Not too long ago we received this Kenwood KA-8300 integrated amplifier in.  The smaller brother to the KA-9800, though differs greatly from the KA-7300 with its 40,000 microfarads of filtering and dual power formers Ken-Trio was known for. Rated at a conservative 80 W/Ch at .1% THD the KA-8300 is a great unit, just a bit of a bastard to work on, very cluttered!

Power Supply X00-1650-11
The power supply on this model had been worked on by a previous technician, all the wire-wraps on the later taps had to be removed and re-wrapped and soldered, someone had simply tacked them in! The original MY4 was pulled and replaced with a low noise Omron DC24 MY4 type. All the electrolytic were replaced with high temp (105C) Panasonic FC’s along with a 100MFD Nichicon MUSE Bi-polar type. Several folks reported imminent  failure of the 14V DZ1/2 diodes which were replaced with 1N5244 type, along with DK3/4 Wo6B to ultra fast #004 type diodes.  Some of the resistors here were removed and replaced, significant voltage is dropped here creating a large amount of radiant heat evident on the PCB so these traces were reflowed as well and cleaned of flux and debris. 

Drivers X07-1420-10
The drivers are a fixed bias A (initial Gain) /B PP topography which utilized the big TA-W100 Darlington IC package where as Q1/2 are our 1st order gain, Q3 our class A operational „3rd order“ driver and Q4 the constant current device for IC1 or the TA-W100 fixed bias network. Differential pairs were updated to matched Hfe 992 TO-92’s. Electrolytic were replaced with high temp (105) low impedance type PW Nichicon’s and high grade WIMA polypropylene for small value capacitors (1 & .22) the input .22 was replaced with a PP WIMA under the PCB and a .47 Panasonic polypropylene ECW coupling film capacitor.  The pins to the TA-W100 were reflowed and new thermal compound pasted on. 

TA-100W (Sanken OPT DIA.)

Pre-Amp X08-1440-10 & Switching/Filtering PCB X13-2220-10
The Pre-amp initial drive is configured of a complimentary Class a design in tandem with two TA7129P Pre-Amp FET’s  which consists of a 3 packaged BJT array in a 7 SIP device. 
All the electrolytic were replaced with high reliability low impedance Nichicon PW and Nichicon Bi-polar, films and lower value 1/.47 MFD tantalums were replaced with high grade WIMA polypropylene film capacitors. 

Presence and Meter Amp X11-1330-10
This is the only location any adjustments are made, as to the meters here for a 4.9V (3.008W) output confirmation. Electrolytic on both PCB’s were replaced with high reliability low impedance Nichicon PW’s and original germaniums held. 

Two new screw type with custom spade terminations were installed, both filter were replaced with a high grade , low ripple Nippon 18,000 microfarad capacitors. 

Audio Notizen beim 4.5 precision 10Khz
0.19 dB difference at rated output
2.85 (1.8W
8.09 (14.54W
11.07 (27.23W
16.00 (56.88W
19.32 (82.94W 49.187dB

3.01 (2.01W
8.15 (14.7W
11.02 (26.98W
15.81 (55.54W
18.90 (79.38W 48.997dB

1 comment:

  1. Great post , I have a pioneer a-7 want to restore it big time . Currently being repaired though first