Olympus OM-1 Resistors

jdk01 · Jan 7, 2021

Hi, I decided to open my 3 OM-1 to look at the meter circuits... and I am confused. Some resistors identification rings do not match the actual resistance. There are also resistors which look like "body-end-dot" or "body-tip-spot" (are they really?) that do not match the actual resistance. Is this just me and my inability to read the rings and dots? Were they productions errors? Also circuits seem not to match those published in 1970 repair mag and Om-1 Service Documentation.. perhaps I need new glasses.. comments appreciated!

shutterfinger · Jan 7, 2021

Black 0; Brown 1; Red 2; Orange 3; Yellow 4; Green 5; Blue 6; Violet 7; (edit)Gray 8(edit); White 9.
Start at the band closest to an end of the resistor. No 5th band 20%; Gold 5%; Silver 10% tolerance.
Newer resistors made into the circuit board I have no clue about.
Color bands fade or change with heat. Some resistors may have a different 5th color band for 1% tolerance.

Pentode · Jan 7, 2021

shutterfinger said:
Black 0; Brown 1; Red 2; Orange 3; Yellow 4; Green 5; Blue 6; Violet 7; White 9.

Grey: 8

When you say "do not match the actual resistance", what do you mean by "actual resistance"? Do you mean the resistance listed on a circuit diagram or do you mean the resistance as you measure it with an Ohmmeter? If the answer is Ohmmeter, are you measuring them in the circuit or removed from the circuit? If they are still soldered into the circuit you will not get an accurate reading. Also, sometimes resistors are combined in series or parallel to reach a non-standard value. You may know all this already; I don't know your electrical background but I'm just throwing it out there.

monopix · Jan 8, 2021

I've often found actual circuits that don't match the manual. I guess they just got updated and the manual didn't.

jdk01 · Jan 8, 2021

shutterfinger said:
Black 0; Brown 1; Red 2; Orange 3; Yellow 4; Green 5; Blue 6; Violet 7; (edit)Gray 8(edit); White 9.
Start at the band closest to an end of the resistor. No 5th band 20%; Gold 5%; Silver 10% tolerance.
Newer resistors made into the circuit board I have no clue about.
Color bands fade or change with heat. Some resistors may have a different 5th color band for 1% tolerance.

Thank you...

jdk01 · Jan 8, 2021

monopix said:
I've often found actual circuits that don't match the manual. I guess they just got updated and the manual didn't.

Thank you for your interest. Yes.... I am hoping to discover updated circuit diagrams to confirm my understanding of what I have.

jdk01 · Jan 8, 2021

Pentode said:
Grey: 8

When you say "do not match the actual resistance", what do you mean by "actual resistance"? Do you mean the resistance listed on a circuit diagram or do you mean the resistance as you measure it with an Ohmmeter? If the answer is Ohmmeter, are you measuring them in the circuit or removed from the circuit? If they are still soldered into the circuit you will not get an accurate reading. Also, sometimes resistors are combined in series or parallel to reach a non-standard value. You may know all this already; I don't know your electrical background but I'm just throwing it out there.

Hi,

Thank you for your interest. The resistors have been removed from the circuit and read by 2 different mutlimeters.

After much frustration with myself, I now believe/realise that some resistors use the the 5 band code without the tolerance being shown. I think this explains all circumstances, except for one resistor with a coding of brown, black, grey, orange (blobs of colour and not rings) with an actual value of 10.89K....

jim10219 · Jan 8, 2021

jdk01 said:
Hi,

Thank you for your interest. The resistors have been removed from the circuit and read by 2 different mutlimeters.

After much frustration with myself, I now believe/realise that some resistors use the the 5 band code without the tolerance being shown. I think this explains all circumstances, except for one resistor with a coding of brown, black, grey, orange (blobs of colour and not rings) with an actual value of 10.89K....

It's probably a 5 band color code without a tolerance marking. So you only have four, but it should be read as five. And the orange is probably red that's just faded.

jdk01 · Jan 8, 2021

Thank you!

Olympus OM-1 Resistors

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