My apologies for writing in English on this German forum. My German is a little rusty
Let me tell you about my experiences with my TC45/4.
After restoring a couple of recordplayers and a Akai GX-77 tape machine, I told my wife I was interested in a new project. No middle of the road device, but something special. As it happened, she found a Braun TC45/4 that looked very interesting to me. I didn't know anything about the device other than 1) I liked the design 2) I found the service manual.
So decided that I would buy it.
When it came, it was in rather rough shape, clearly it hadn't been used for a long time. Also the face place damaged. Some text was gone, it had stains all over, the colour has damage.
After opening up, I was very impressed with what I found. It turned out to be a really well designed and built device.
Next, I unplugged everything from the power supply and slowly started it up, first a couple of hours 110 volt, next 230 volt. Next the same procedure for the power amplifier, and the rest of the board. Nothing exploded...
The device seemed to work somewhat. But off course there were several issues.- Tuning capacitors were completely stuck.
- The wires for the dials broke the first time I tried to turn the tuning knobs.
- The preamp clearly was not working as intended anymore.
- Same goes for the power amp.
- Stereo indicator wasn't working.
- The small lights were broken.
- The record player was a real mess.
I decided the device was in good enough shape to try a restoration.
First things I did was to get the tuning capacitors going. A repeated treatment with isopropanol, sewing machine oil and gently applied force did the trick.
Next, I spent a full evening installing nylon wire for the tuning scales. Eventually both the tuners worked very nicely. I didn't bother testing the tuner for short- middle and long wave since it has no practicle use anymore. The FM tuner however turned out to be surprisingly good.
Next, I decided to check every elco and every resistor on every board. This of course took some time. I found that the majority of all elco's were in great shape. Some of the smaller elco's were out of spec or simply dead. Also I found several resistors way out of spec.
The hardest part turned out to be the power amplifier. Before recapping it worked reasonably well. After recapping it didn't work at all. Bias current was about 500mA instead of 25mA. I thought I broke it, but I could not think of how. I measured the transistors and got strange readings. I concluded that the AD131 transistors were dead. I could not find replacements anywhere, instead I ordered a couple of AD149. Next I had a close look at the driving stage. The transistors were OK, but I found a couple of resistors out of spec. I concluded that these resistors caused fully saturated driving stage and power transistors. Also I concluded that my testing equipment probably was not suitable for measuring germanium transitors, resulting in strange readings. I replaced the faulty resistors and tested the power amplifiers without the power transistors attached. Now the driving stage worked perfectly, so I had found the root of te problem. Finally after reconnecting the original AD131 power transistors, the power amplifiers worked fine.
For the stereo decoder, I found that the PNP transistor that drove the indicator light was dead. It was a germanium transistor, but a BC559 as replacement turned out to work fine.
For the stereo indicator light and the meter light, I decide ona replacement with LED. I used very small LED's from a Christmas light. The stereo indicator light already was DC, so .I used a simple voltage divider to drive the LED. For the meter light I made a small bridge rectifier and to voltage divider form a 10K resistor with parallel 100uF capacitor.
All the intense labour was worth it. I was very impressed with the end result. Using Elac speakers, the TC45/4 sounds very, very nice. The tuner is really good, stereo decoder has very nice sound stage, the amplifier sounds excellent, well balanced, very punchy and powerful. I never had thought that 60's audio equipment would sound this good.
By far the weakest part of the TC45/4 is the record player. At least to my opinion. I cleaned all moving parts and applied new silicon grease and sewingmachine oil. I also took apart the motor. The idler wheel was the big issue. It was hard and developed not enough traction anymore. Since I could not find a replacement anywhere, eventually I decided on a adventures solution. I got a few inner tires for bikes. A 5 mm wide slice fits around the idler wheel. I glued it to the original wheel with some rubber cement. It works sort of. The original idler wheel itself is not perfectly round and makes noises louder than the sound which the motor produces. To my ears the rotation of the platter is not stable enough. But maybe this is just the best an idler wheel record player can do. Maybe I am spoiled because of my direct drive Denon DP-47f.
Final stage in the project is the paint. There are three options:
1) Keep it as it is.
2) A complete repaint of the original case and face plates. This means getting thing the case and place plates sprayed in the exact right colour by a car painter. Next make a new design for the text and lines on the computer. I found the Braun font which is a good starting point. Finally think of way to apply the text on the freshly painted face plate. Originally this was done using screen print, but that is really expensive. Alternative method could be waterslide decal paper. But it's hard to get good results this way. Also it needs a laquer top coating, which could be too glossy.
3) Make complete new face plates.
Being Braun fans, I am interested in your opinion and suggestions.
