Back in the 1960’s in my teen age years, my buddies and I had the wonderful privilege and fun to build electronic kits. The kits that we mostly built were the Knight Kits of Allied Radio and Heathkits. How fun it was to receive the kits and check them over looking at all the parts. Then we begin to assemble and solder the projects together. The early 60’s was the transitional time when there was a mixture of tube and transistor technology. The first generation transistors were made out of germanium. Later came silicon which could handle more power. But with the latest research it looks as if industry will return to using germanium again.
The kits that we built the most of were for stereo listening. The first two kits that I built were tube stereo audio amplifiers. Later came a transistor FM receiver. What great fun!
I have sold or given away my early stuff, but just recently I came across a Knight Kit Amplifier that was in a nearby community. Even though it wasn’t working I thought it would be fun to see if I could get it to working again. All the old electrolytic capacitors were replaced and then I turned it on. Smoke boiled out of it, yipes. It turned out that both output transistors had been shorted and the 40 volt supply was going to ground through their two low ohm emitter bias resistors.
A friend of mind who has a communication business gave me the two replacement transistors. After installing those the amp sounds great. The scorched bias resistors will need to be replaced in the future but it sounds good enough for now.
The modern amps are wonderful, but there is a certain satisfaction in listening to old equipment that we personally have worked on and have a knowledge of how the circuit works. I have enjoyed playing CD’s and Records immensely on this old amp. It makes me feel young again and brings back great memories of the music of the 60’s.
The amp that I just repaired was a knight-kit KG-854 stereo amplifier. I had a difficult time finding a schematic (wiring diagram) for it, so I thought I would include a picture of the schematic here. Perhaps you might be looking for the wiring diagram as well. For higher resolution I took two pictures, one of each side of the schematic. Zoom in on these and see if you can read them. If you cannot read them clearly, email me at [email protected] and I will email you the 1.5 meg high resolution images. For some reason when I try to upload the high resolution image, this web builder reduces the resolution.
Good News! Below is a link to a website that has nice clear circuit schematics and a manual for the KG-854.
The early 60’s were the age of elemental components: resistors, transistors, diodes, capacitors, and tubes. There were almost no integrated micro circuits. The old stuff is very straightforward to troubleshoot.
Always remember! Troubleshooting old tube equipment requires safety precautions and procedures. Tube equipment can have voltages around 400 volts or higher, and can kill! Even when turned off and unplugged, the electrolytic capacitors can still hold hundreds of volts. Just as working with anything that has power, please be careful.
Thanks and God bless you.
Schematic of Knight Kit KG-854 Stereo Amplifier