You see the Frako caps in a lot of expensive / respected gear. I've seen them in Neve gear from the same era. They are also seen in B+K test gear (again, a good example of decent design, but long term reliability is hobbled by poor component choices). I have no idea why respected OEMs fitted the Frako... They can go really low in R and cause mayhem.
During the initial inspection of the preamp, I noticed two red tantalum capacitors that were fried. I replaced them immediately in both units. They were 22µF 35V caps, which I swapped out for long-life alternatives. Interestingly, these same tantalum capacitors were commonly used in the Studer B67 and Revox A700 — especially on the tape control board and in the IC bus — where spot replacements were also frequently needed. Fortunately, this failure didn’t damage the preamp; it simply disabled the mute function, which was resolved after the replacement.
Overall, the capacitors used in the preamp are of high quality, and I don't plan to replace them unless one fails. However, I can't say the same for the power amp — it runs hot, around 55°C. My initial inspection focused on components that are known to short or burn out, like the failed tantalums. I’m less concerned about parts that degrade quietly and slowly over time, such as the old blue Philips capacitors or the black ROEs.
Overall, the capacitors used in the preamp are of high quality, and I don't plan to replace them unless one fails. However, I can't say the same for the power amp — it runs hot, around 55°C. My initial inspection focused on components that are known to short or burn out, like the failed tantalums. I’m less concerned about parts that degrade quietly and slowly over time, such as the old blue Philips capacitors or the black ROEs.
Attachments
Solid Tantalum capacitors were normally recommended for timing applications. They never see high voltage spikes there, high currents (it is actually low) and so a good application since they are supposed to be low leakage. Too bad they are not reliable at all.
A normal modern electrolytic should be fine. Size might be an issue.
A normal modern electrolytic should be fine. Size might be an issue.
I remember I did a search for a replacement and found that the KEMET T350 Series Tantalum Capacitors - Solid Leaded but prices are so expensive compared to Electrolyte Capacitors.
See if the solid state electrolytics used in computer motherboards are available in the rating you need.