Hi. Ever since I’ve had this Conion C-100, I’ve had a problem with recording. It records very quietly. Playback seems fine. I’ve been looking for the cause of this for a long time, but everything looks fine. Ultimately, I suspect the head is damaged or worn out. I’m attaching a photo of it that was taken when I took this Conion apart for inspection. Does its appearance indicate significant wear? What specifications should a replacement have? I have a Hitachi TRK-8800E and an Aiwe Cs-600, from which I might be able to get a head. Would that work? Translated with DeepL.com (free version)
The head does appear to have some wear (there is a visible groove) and also some surface rust/corrosion. The surface rust/corrosion could affect recording, although it should also affect playback to some degree. A replacement should, first of all, fit mechanically and sit at similar height and depth compared to original. Then it should have similar resistnace of coils and inductance. Can't say if the mentioned Hitachi TRK-8800E or AIWA CS-600 fit, as I'm not familiar with any of the models. However I would recommend lapping or polishing the original head rather than replacing it. Problem could also be caused by electronics, in particular lack of bias signal (open bias trap coils, etc.).
Thanks for the reply, Valentin! The photo I posted earlier was taken after he arrived at my place—before I cleaned it, etc. Of course, I cleaned the heads as best I could. I didn't polish them. I mentioned that it plays back correctly. More or less correctly. The recording is barely audible, almost nothing. But when I set the playback switch to Metal or Chrome, it’s a little more audible. Manually adjusting the recording level helps a bit. I tried checking the circuits, etc.—it looks okay at first glance. But I’m already going crazy over this. My head is spinning. The upper deck plays fine. I’ll attach photos of the head as it looks now after cleaning. I also peeled off the metallic sticker from the head to see what symbol is on it. I’ll also attach the schematic and ask that, if you have the time and feel like it, you mark on it what to check. It would be great if this C-100 were fully functional. Link to schematic CONION C100 SCHEMATIC Service Manual download, schematics, eeprom, repair info for electronics experts
Would start with polishing that head, it's really rusty. Fact you get stronger singal on chrome/metal bias suggests either the bias is too low (bias is higher with metal/chrome) or the tape/head contact is very poor.
What polishing technique do you recommend? How do you do it? I'll give it a try. By the way, I'm going to buy a new head. Do you think this one will work? TELEFUNKEN Tape Head 223-30 for Hifi Tapedeck Hör-sprech Head New | eBay or Unknown Make 223-30 12.5K N6920 Record Playback Cassette Tape Heads Qty 2 NOS | eBay
The 2 heads in the links look almost identical to each other and by the looks of it almost identical to the one in your boombox. So chances are any of the 2 is a good replacement. As far as polishing goes, depends what you want to achieve. If only the surface rust/corrosion is to be removed, using a Q tip and rubbing it against the head by hand can be enough. However this head has a pretty deep groove also and, in my opinion, requires lapping polishing not being enough to restore it to original specs. But if you are going to replace it, the lapping/polishing can be something to exercise on later.
I noticed one more thing that might explain why the recording is barely audible. When I press the Rec button, there’s a crackling sound in the speakers that lasts a fraction of a second, and this is also visible on the VU meters. The same thing used to happen when I first switched the selector to Stereo Wide mode. And as far as I remember, some capacitor was responsible for that. So maybe, aside from the fact that the head is a bit worn to some extent, the main cause of the weak recording signal is primarily a faulty capacitor? Could you take a look at the schematic because I can’t focus on analyzing this? Translated with DeepL.com (free version)
The crackling you hear is likely related to a dirty REC/PB switch (which could be related to your problem), not to capacitors. Generally speaking, wouldn't necessarily suspect capacitors unless the unit uses a brand that's known to have had problems (Nichicon, Matsushita). Could it be capacitors ? Yes, but chances exactly 2 in the rec signal path failed (and nothing else) is slim. Best approach would be to start measuring the signal path with the oscilloscope. I can help with that, assuming you have an oscilloscope. Looked at the schematic, but can't tell what's wrong just by looking at the schematic. You need to do some measurements. Otherwise, by guessing it may take a long time to figure out. But polishing that head is an easy thing to do, at least you can confim/eliminate it as a potential problem.
I cleaned that long switch on the board by spraying it with a suitable cleaner and moving it back and forth many times. I have a mini oscilloscope, the FNIRSI DSO-TC4 . This head can’t be cleaned any further using cotton swabs and isopropyl alcohol. Unless I use some kind of model-making micro-polisher, but I don’t think that’s the point. An audio head I bought on eBay will be arriving soon.Mine is definitely worn out to some extent. But I suspect that’s not what’s causing the main problem.From what I can see, someone replaced a lot of the capacitors with Chang brand ones at some point. Translated with DeepL.com (free version)
