Hi, when I introduced myself here in 2017 (infected with the Walkman Virus), I mentioned, that I owned many years ago some nice Hi-Fi stuff, that I was flogging for iPods etc. I regretted giving away one device in particular: A Technics RS-B100 tape deck. A few years ago, I finally found one again on ebay at a reasonable price. It had the usual issue with the idler wheel -easy to fix thanks to Marians idler tires. After almost 40 years the deck now shows symptoms of old capacitors: The sound image has become flat and the record levels are not constant anymore. Although the change of the capacitors is far beyond my skills, I would like to give it a try. I found a German site with excellent photos of the RS-B100 and other beauties. The guy (pearldragon) mentioned that he changed every single of the 127 capacitors. In the SM parts list the number is more than 200 capacitors (most of them electrolyte). Finally, I found a recap kit with 78 capacitors here: https://www.audio-high-store.com/product/technics-rs-b100-upgrade-kit-audio-capacitors/ Has anyone here ever recapped the RS-B100 and/or know this kit or could provide some advice or even an “order list”? Any advice or help is very welcome. Thank you.
From what I can see this unit is a dual-capstan one. Given this, it is worth checking/replacing both pinch rollers to make sure the tape tension is good. Seems there is a problem with not erasing caused by this (link below). Record levels not being constant can have a similar cause, so it's something to be checked. What do you mean by "sound image has become flat" ? Lack of bass ? Lack of treble ? Please describe in more technical terms, cause it's not clear to me what you're reffering to. https://www.tapeheads.net/showthread.php?t=37410 https://www.tapeheads.net/showthread.php?t=80998 Given the other thread above, where A.N.T. audio was commenting about the deck, he mentions nothing about caps being a common problem on this unit. "The guy (pearldragon) mentioned that he changed every single of the 127 capacitors" - did he had the same problem and changing caps solved it ? Please provide a link for reference, we can translate it with Google/Bing. I would not jump at changing the caps (given how many there are) unless I am sure that is indeed the problem. Can you provide pictures with the inside ? What brand are the capacitors ? Some close up pictures would be helpful. Despite the fact that electrolytics capacitors do degrade over time (usually manifesting by decreased capacitance and increased ESR), this degradation is not always significant and they are far from being such a common problem in old electronics as people tend to think. I have measured many old capacitors on LCR meter and I have seen many that measure same or even better than new ones in some cases (I'm reffering to good brand new caps, not Chinese knock-offs). Most electrolytics have a +/-20% tolerance on the capacitance value anyway (which is taken into account in design), so having a 5% drop in capacitance won't really make much of an audible difference, if any. However, a calibration is recommended after fixing the problem.
Thank you Valentin for all the advice and sorry that it took me so long to reply. Pinch rollers have been replaced in 2018 (but not the capstan belt). Erasing and tape transport work fine. Only some pre-recorded cassettes have a problem with the tape transport. So I suppose its more a problem with the band material of pre-recorded cassettes. Record and playback level can be calibrated manually with this tape deck in order to have equal record and playback level. In my case, "flat sound image" means, that this is not possible anymore (playback level is much lower than the input level) and that regardless of the bias adjust, the sound is dull (heads are clean). I tried a record with the same cassette and the same sound material on my RS-B965 with a much better result, so there is definitive something to be checked. Here is the link to the beautiful site of "pearldragon": https://www.pearldragon.de/hifi/rs-b100/ By chance, I found someone close in my neighbourhood who knows a lot more about electronics than I do and is willing to take a look at the tape deck. I hope to be able to report soon on what the next steps are to get this beautiful deck working properly again. In any case, your experience with capacitors makes me optimistic that the exercise of replacing the capacitors may not be necessary after all. Thanks again Analogtape / Konrad
Thanks for sharing the link ! It is a very complex deck by the looks of it. Those dbx/Doby encoding and decoding cards are large. Really like the detailed description by pearldragon ! In regard to pre-recorded tapes, yes, usually the tape material used in those is not of the highest quality. I now understand what you say with "flat sound image". Given the complexity of the unit, I can't pinpoint anything specific. As for capacitors, I now see in the pictures many of them are CE brand. Despite the fact that I have seen those leaking in some walkmans (those had much smaller footprint though), I can't see any sign of leakeage on those pictures. It is likely that these larger ones do not have problems, but I may be wrong. I have certainly seen this brand in other devices than those problematic walkmans (JVC CQ-1K and Infinity Intimate Stereo) working just fine. What I would do if I were to repair this myself is take it step by step: - measure the bias signal amplitude at the head; see if it varies (enough) when rotating the bias knob; see if by adjusting the internal bias trimpot I can bring a 10kHz -10dB signal to also be -10dB on the tape; - if the bias amplitude does not vary enough to make the 10kHz signal equal with the source, I would start looking from the head backwards: AC bias trap, rec EQ amp, bias oscillator, etc. I certainly can't gurantee the caps are good, but starting by replacing them all is not a wise idea (especially when there are no signs of leakeage), that is what I was trying to say in my previous post. Glad you found someone who can help you in repairing the deck ! Please do let us know what you find ! I'm curious myself and it will be a reference to others reading the thread as well. Feel free to ask more questions if you need help.
