I am restoring a Gonset GSB 100- Have replaced the caps and tested the Tubes. However I have been unable to stabilize the Bias setting on the 6DQ5. It will not stabilize at 20 MA.

Title: gonset_gsb_101_chassis.PDF Author: Bay 6 Created Date: 7/29/2006 8:08:38 PM.

It turns on and will climb up to the scale untill it maxes out. I have replaced the the negative Bias Diode with a 1n1007 and verified the 135 Volts from the Transformer. Removed the Bias adjust pot - cleaned and tested OK at 289 K OHMS. Does any one have an idea on the possible fix or trouble shoot direction. You help would be greatly appreciated. Thank You For Reading My Post. As Geoff noted the tube is often the cause of this problem.

Either gas and/or secondary emission are common causes of this behavior. The GSB-100 seems to have an issue with power transformer failure so treat it gently if you still have the original transformer in place. It is a nice vintage transmitter and the unique (for a transmitter) single crystal notch circuit really does work well for improved carrier suppression. My GSB-100 is less fussy than my CE 10 and 20 series exciters about adjusting carrier balance during warm-up. I have one paired with a GSB-101 amp and HQ-170 and that setup makes a very capable all-mode vintage station. Tom, The bias voltage sounds way too low to me, I would expect more around -50 or so to set the proper idle current.

I am wondering whether your GSB-100 meter is accurately reading plate current. With the power off and the transmitter meter set to the RF output position (to take it out of the plate current circuit) measure the resistance of the 6DQ5 cathode resistor, it should be 10 ohms. Then leave your meter set to measure DC voltage and measure the voltage indicated across this resistor when the internal meter is indicating 20 mils of final current. Tom, Try it with the meter switch in the output ind. Position, otherwise the internal meter will be in parallel confusing the measurement.

At 20 mils of current you should expect to see only.2 volts across the cathode resistor,. Microsoft Office 2007 Download Gratis Em Pt Pt Completo Toronto more. 584 volt would indicate actual current flow of about 59 mils at idle and this would result in very fast tube heating with the likelihood that it would then start to draw even more current and would go into a destructive cycle if you didn't shut it down quickly. Hello Tom, You mention that the cathode resistor was burnt when you got it, so it would seem this isn't a 'new' problem. As Rodger mentioned, you do want to be nice to the power tranny because they were about a buck eighty five when I replaced mine 3 years ago, and I suspect Hammond wants lots more today. I haven't seen any mention of the positions of the various controls such as carrier level, or operational mode. I presume you are in SSB mode and the carrier level is at '0'.

Did you perform the carrier null process on page 13? This transmitter has a very good carrier null and is quite stable as Rodger mentions. Is the Screen voltage constant at +150 Volts with the final in(Tx) or out (pulled)? Dbt Skills Training Manual Marsha Linehan Borderline. Did you measure the value of the final's 100 Ohm screen resistor? Have you pulled the final and monitored the bias voltage in Tx mode?

I agree with Roger the bias should be around -50 volts. Have you cleaned the SW2-B wafer contacts? Are You Experienced 1967 Rar. Have you replaced the 100 puff cap between the driver output and the final's grid? Kind of a shot in the dark, but.

At this juncture, I think I'd pull the final and monitor the drive level from the 12BY7 and see if it remains constant, or slowly rises. If the drive slowly rises, your 'Final problem' is elsewhere. My vote would be the balanced mixer, or the notch filter. I got mine six years ago and it had a problem with the Notch filter, and once fixed this transmitter has been trouble free. The notch filter is shown as another 'Area 51' on the schematic, but if its broke, I couldn't make it any worse, rite? _________________ Bold text & pics are usually links.