Strange capacitors in PYE 84571/01 Compression Amplifier. Tantalum? Color coding? Manufacturer?

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Bjorn Andersson

Bjorn Andersson

Active member
Joined
Mar 1, 2013
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32
Location
Sweden
Is there anybody on the forum that recognise those strange looking capacitors?
Tantalum? Color Coding? Manufacturer?
I have never in my life seen any of those capacitor. :oops:
Did PYE perhaps made them?
I can see one regular drop shaped tantulum capacitor (C2 on the right side of the pcb).
 

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Reading from the bottom up on the close-up looks like 6-blue, 8-grey, 5-green plus 2 for the red on top maybe unless the red is just marking the + end - could be 6.8 uF 2% - on cylindrical caps there are often four bands - 1st#, 2nd#, multiplier, tolerance. Like resistors.
 
RoadrunnerOZ said:
Reading from the bottom up on the close-up looks like 6-blue, 8-grey, 5-green plus 2 for the red on top maybe unless the red is just marking the + end - could be 6.8 uF 2% - on cylindrical caps there are often four bands - 1st#, 2nd#, multiplier, tolerance. Like resistors.
Click to expand...
That seems to be right (6.8uF).
Regarding to Khron´s link: https://www.engineersedge.com/instrumentation/capacitor_color_codes.htm
Found that value on C28 on another fuzzy schematic (probably a PYE 4060 Comp). :)
 
RoadrunnerOZ said:
Reading from the bottom up on the close-up looks like 6-blue, 8-grey, 5-green plus 2 for the red on top maybe unless the red is just marking the + end - could be 6.8 uF 2% - on cylindrical caps there are often four bands - 1st#, 2nd#, multiplier, tolerance. Like resistors.
Click to expand...
Back in those days, nF was not in common use. Many caps were specified in pF so this could be 6800pF or 6.8nF - much more likely value to be a 2% part than a 6.8uF

Cheers

Ian
 
ruffrecords said:
Back in those days, nF was not in common use. Many caps were specified in pF so this could be 6800pF or 6.8nF - much more likely value to be a 2% part than a 6.8uF

Cheers

Ian
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685 is 68 x 10*5 is 6,800,000pF - 6.8uF - 6.8nF would be blue, grey, red - but we have the green in between the grey and the red which doesn’t equate to a sensible value. Also the cap is polarised from the markings on the pc board making it some form of electrolytic. Easy way is to pull a cap and measure it.
I think the red spot is a polarity marker or it would probably be in line with the other 3 dots and on the side.
 
Some early tantalums had odd casings - in an old Moog I’m servicing they use some that are black tubular axial with one end rounded and others that look like axial can electrolytic with a clear plastic tube cover - these all blew when someone plugged in the unit to 240V when it was set to 110V.
 
RoadrunnerOZ said:
Some early tantalums had odd casings - in an old Moog I’m servicing they use some that are black tubular axial with one end rounded and others that look like axial can electrolytic with a clear plastic tube cover - these all blew when someone plugged in the unit to 240V when it was set to 110V.
Click to expand...
Jesus!I I will measure the C28 cap and inform all of the value ;)
:oops:
 
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The value of the C28 capacitor is 7,02uF and then i found out that that the TO-3 power transistor is broken in the PSU and the power supply was putting out approx 30 Volts to the electronics... And after that i found that someone have been cutting out transistor VT3 from the circuit... I put a substitute transistor in place of VT3 and then slowly ramped up the voltage to +16 Volt and the compressor works. Current consumption is about 180mA and the VT7 and VT9 output transistors gets to about 69 degrees with mounted heatsinks on them. :)
 

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Bjorn Andersson said:
The value of the C28 capacitor is 7,02uF and then i found out that that the TO-3 power transistor is broken in the PSU and the power supply was putting out approx 30 Volts to the electronics... And after that i found that someone have been cutting out transistor VT3 from the circuit... I put a substitute transistor in place of VT3 and then slowly ramped up the voltage to +16 Volt and the compressor works. Current consumption is about 180mA and the VT7 and VT9 output transistors gets to about 69 degrees with mounted heatsinks on them. :)
Click to expand...
7.02uF is within 5% of 6.8uF, so I think it’s fair to say that was probably the correct marked-value.

In any case, congrats on getting it up and running!
 

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