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Old 05-26-2017, 12:13 AM
Crist Rigott Crist Rigott is offline
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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.
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Old 05-26-2017, 05:54 PM
Crist Rigott Crist Rigott is offline
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I'm trying to ID a Zener Diode. It is CR-5 in the parts list with a number SZ11714. Here is a section of the schematic where it is used. Any ideas what it is? Thanks.

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Old 05-27-2017, 11:47 AM
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Notimetolooz Notimetolooz is offline
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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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Old 05-27-2017, 09:46 PM
Crist Rigott Crist Rigott is offline
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Quote:
Originally Posted by Notimetolooz View Post
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.
Cool! 24V 2W. Thank you.
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Old 05-28-2017, 08:58 PM
Crist Rigott Crist Rigott is offline
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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
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Old 05-29-2017, 10:19 PM
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Notimetolooz Notimetolooz is offline
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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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Old 05-29-2017, 10:25 PM
Crist Rigott Crist Rigott is offline
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Quote:
Originally Posted by Notimetolooz View Post
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.
Thanks Tim. I see the post on the other Forum. Been very busy lately with family.
I'll try the cap and the resistor too when I get around to changing out the E-caps first. Maybe this coming week.
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Old 06-01-2017, 01:21 AM
Crist Rigott Crist Rigott is offline
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What kind of diodes are these? The parts lists them as Silicon with a number of FR-1P.

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Old 06-01-2017, 10:28 AM
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N2IXK N2IXK is offline
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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.
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Old 06-01-2017, 05:40 PM
Crist Rigott Crist Rigott is offline
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Great. Thanks.
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