Tuesday, June 14, 2011

Carbon Composition Resistors in Buchla Gear

The 258C seems to have random population of CCs, but the 258B schemo specifically indicates certain values to be carbon comp:

1, 2.2, 4.7 multipliers (10R, 1K, 10K, 100K, 10M, 2.2R, 2.2K, 470K, 4.7M).

In the last post I note that the 158A indicates that some resistors should be 10%.

"On the CBS schemo, note that some resistors are 1%, and some are specifically listed at 10%. These are at a glance, 1.0, 2.2, 4.7 multipliers, and include the 330K as well (which also appear in the sine shaper). Unremarked resistors are stated as being 5%. I note that the 258B schematic lists all 1.0, 2.2, 4.7 multipliers as being specifically carbon composition types, all others tin oxide. I wonder if you looked at a 158B/CBS/Tape Music Center unit if all of these would be Allen Bradley or other carbon comp."

I also note that the CBS 106 mixer schematic lists many resistors as 5%, and the rest as being 10%. Again, these are the 1, 2.2, 3.3, 4.7 multipliers (1K, 10K, 220R, 2.2K, 330R).

I've asked a 158 owner for a pic to see if they are there...

If you are on prodigy-pro.com/diy or other higher-end gear pages, you will note that carbon composition resistors are spoken of highly. I note that on audiophile DIY sites that it goes further, with tantalum resistors being the item of choice in certain critical places in the signal path, especially in circuits with gain as it is said that tantalums have no thermal noise, as do metal film resistors. Then again, tantalum resistors seem to start at about $3.85 each, and go up to around $10.00 each.

I note that since these are vintage components, they can suffer from slight oxidizing on the leads. A slight rub with loose steel wool right up at the resistor body will clean these up quickly.