#1
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Knight KG-687 Sweep/Marker Generator
Guys,
I could use an Operator's Manual. I have the assembly manual and a schematic. Also does anybody know if the test leads that are coax is it RG58? Thanks. |
#2
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#3
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I can reverse engineer it. So you know it is a 24V zener. From the current through R61, 40V-24V= 16V. 16/220 = 72.7 ma. If the circuit fed by the 24V was removed, (some kind of a malfunction), the zener power dissipation would be 24V X 0.0727A = 1.745 W. Call it 2 Watt. So look for a 24V, 2 W zener. Mouser has a 2EZ24D5-TP by MCC. This might be overkill but at least it could handle the current if something goes wrong.
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#4
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Quote:
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#5
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I'd like to add a BNC so that my frequency counter can read the marker frequency. However I have no idea as to where to "pick off" the signal. Below is a link to a hi-res schematic of the KG-687. Maybe somebody with a lot more knowledge can use the schematic and figure it out.
Many thanks. https://www.dropbox.com/s/d9uq4v8zda...matic.pdf?dl=0 |
Audiokarma |
#6
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I believe someone on the other forum suggested the point between C18 and R33. That seems reasonable. If you have a scope you can check, if the scope can display the frequency well enough. Also you could just try a makeshift connection to your counter. It would probably be a good idea to put a 100pf cap in series with the connection to the counter for DC blocking and isolation. If the signal is large enough, a 100 ohm resistor in series with the line to the BNC would help isolation also, so the counter doesn't load the marker so much it doesn't work right.
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#7
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Quote:
I'll try the cap and the resistor too when I get around to changing out the E-caps first. Maybe this coming week. |
#8
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#9
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Look like typical 1960s/70s Japanese silicon rectifiers. I believe the manufacturer was "Origin".
Should be no problem replacing them with a generic 1N4007. |
#10
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Great. Thanks.
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Audiokarma |
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