Only electrolytic cap will dry out but most of them in here is for by pass , if they were bad , will more hum or distort, all coupling caps are tantalum cap , most are 47uf , in my modification was change to better one without polarity (Solen) has a very good result , but it is too big can't put into the card has wire out
tony ma
Hi HJ,
It seems your B62 had been upgraded and newer audio cards were installed in its later life. The audio boards you had shown are compatible with A80RC. Although there had been further improvements from the version you have, it looks good from the photo. The younger audio boards would have the A101 "opamp" made of discrete transistors and other parts in a small daughter board instead of the blue colored potted device you see in all of the photos. Even the potted A101 amps have evolved. There are two kinds - one potted kind with simpler discrete parts and newer version with surface mounted parts that are thinner.
There is a C40 (470pF) Polystyrene cap near the edge connector (from my memory...it is tied to the C6 and to the signal ground). I recommend replacing it with 150 pF to use with modern hot tapes such as ATR and RMR900 to increase dynamic headroom in record bias and HF response.
Yes, I didn't show the EQ boards. The particular A80RC audio card would have modified EQ board for 15 ips in IEC EQ but 7.5 ips in NAB to play commercially available two track tapes. I once was pleasantly surprised at the A80RC machine's performance even at 7.5 ips NAB using RMG900 tape properly calibrated. It certainly sounded as good or better than other average master recorders running at 15 ips. bottom line, you should get an A80RC.
Tony is correct, I would recommend all yellowish Frako electrolytic caps to be replaced with modern kinds before one of them would short out your power supply or literally blow up in smoke! I like Panasonic or Nichicon or I use other esoteric caps with very low
ESR (Equivalent Series Resistance) and similar size.
I had various discussions over the years with true Studer experts around the world (whereas I am a fake) on the virtues of the Tantalum caps (blue and green tear drop shaped caps) in Studer audio boards. What I had been able to learn was that Studer used them for reliability, form factors, and economic reasons but long use of the Tantalum in their audio circuit had morphed into the "Studer Sound" that some people would defend with vigor. On the other hand, I have talked to other professionals, who think the Tantalum caps are junk and must be replaced. I tried both and can't tell huge differences in sound.
I left them alone in all of Bruce's and my A80RC machines. I figure, if it is good enough for Bruce, it's good enough for me and who's to argue?
