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"but not everyone has one. I may also try your shunt regulator across the primary side idea! P" Take a look at the other topics on this CDV700Club? list P., I have the assembled boards for the CDV-700 hack, either the fixed single or switchable 3 position HV adjust via TL431. Schematic is the post from last week.? If you want to play with one or both or jest need the parts for the LENi Pro conversion, I have those too, in lead-ed and SMD. Don't forget, fiddling with the primary side changes then calibration (only on CDV-700 and close variants) due to the source of the -15V metering circuit. I just use 2 pcs 9V batteries and a 7915 instead for -15V,? if frequent adjustments anticipated, like for changing probes or what not. On the heat gun, I use mine every day. Mostly for heat shrink but probably 100 other tasks on the bench. It's Model 6993 by Weller or Ungar. Already have one for every bench but saw one come up for auction this morning, cheap. If I win it, I'll send it you way too. Thanks for other '431 numbers, wish they had a 60V one, then it could just sit at the bottom of any Zener stack and give adjustable +/- 30 range with almost no parts. Settable max-aqnd min too, and the onboard SET pot can be remoted to the? panel with no worries of catastrophes. Geo ----- Original Message ----- From: peter via groups.io <epkoncept@...> To: [email protected] Sent: Tue, 05 Apr 2022 11:26:10 -0400 (EDT) Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and more.IF th Geo: ?You can adjust the HV shunting voltage by either changing the resistor between base and ground or by changing the value of the zener and or both. In theory, the Vbe temperature coef can be cancelled with a zener with a voltage around 6.2V or so. However, there is also the temp coef of the resistors which can vary +/- last night I hit the circuit with a hair dryer, with cheapo carbon comp resistors for the 66M and a 5.1V zener the voltage when up about 5V? when raised from 25C? to about 50~60C. But the 1M? resistors were metal film. The trimmer and the 100k were cheapo carbon resistors. I was thinking of replacing the original regulator tube in my CDV-700 6a with this circuit. Good enough. Yes, you could also use a TLC431 or was it a 1431 shunt regulator IC inlieu of the zener, but not everyone has one. I may also try your shunt regulator across the primary side idea! P |
