RCA 1861, NTSC and a DEC VR-201

From: Philip.Belben_at_powertech.co.uk <(Philip.Belben_at_powertech.co.uk)>
Date: Thu Sep 30 10:48:06 1999

I think this thread is getting old, but as an EE I think I'd better set this one

>>Yellow-Purple-Gold-Gold resistor, then tied to ground via
>>a Grey-Red-Black-Gold (might be Sky Blue-Red-Black-Gold) and then through one
>>of the rear pots. I would spec the values, but I'm not used to such odd
>>in the significant digits of resistors (just as tolerance bands). Would a
>>EE care to translate these? Might that second one be 92 Ohms? Could the
>>first one be 7.5 Ohms?
> Puzzles me too.
> Silver 1e-2
> Gold 1e-1
> 1 Black 1e0 First 2 digits give mantissa,
> 2 Brown 1e1 3rd digit gives exponent,
> 3 Red 1e2 4th band gives quality of resistor (if present), else +/-
> 4 Orange 1e3 (silver = +/- 10%, gold= +/- 5%, red = +/- 2%)
> 5 Yellow 1e4 5th band (if present) gives reliability (mil-spec, etc.)
> 6 Green 1e5
> 7 Blue 1e6 Example: red-yellow-orange-gold = 2,4,10^3, 5% = 24k Ohm, 5%
> 8 Violet 1e7
> 9 Gray (From Horowitz & Hill, The Art of Electronics, 1st Edition
> 0 White pp. 645-646)

Ouch! No, black is zero, brown is one, up to white which is nine. The values
in the mantissa correspond then with those in the exponent.

Yellow-purple-gold-gold = 4.7 ohms as someone (Pete?) has already pointed out.
Grey-red-black-gold = 82 ohms
Blue-red-black-gold = 62 ohms

All are standard values, though 62 is less common being an E24 rather than an
E12 value (i.e. only used if you're sorting resistors into 24 values per decade,
not if you're sorting into 12)

I would guess that 82 ohms in parallel with the resistance of the pot (which
probably is wired as a potential divider) gives about 70 ohms, so the 4.7 makes
it up to 75, and doesn't let you connect the (presumably sensitive) circuit on
the input directly to the pin. This would imply a pot with resistance 470 or
500 ohms.


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Received on Thu Sep 30 1999 - 10:48:06 BST

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