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yes, give it up on sweep tubes! they are not made anymore.. and give it up on 811 and 572 junk tubes made in China. China (CCP) with their boy Fauci were only good for making long lasting viruses!!!!!! it is even hard to find real working RF NPN bipolar transistors these days. Do not buy from...

I would disconnect the plate high-voltage at the board, or disconnect meter circuit resistor R12. (this resistor usually blows up during a tube failure on these types of amps) a high-voltage probe would be nice to use here to measure. Then "smoke test" also, carefully, and quickly, at the...

I noticed a similar problem on a 2950/2970 main board a few months ago. In the driver transistor bias circuit. I added a 100k resistor to ground. - - from that post: "So looking at the schematic at Q62 there is no resistor going to ground after bias adj pot VR13 to make a correct adjustable...

..... here is a pix of one of the fake 2SC1969 transistors a friend got off eBay. they even have the Mitsubishi logo on them. I think they are some regular low frequency transistors repainted. They do not work very well at 1.9 MHz and forget it up at 28 MHz. I also have some Motorola...

funny, I was gonna call ICA today. a guy sent me 7 2SC1969's from different eBay sources, and they all are fake. do not work. they barley work way down at 1.8 MHZ. this is for a 1.8 to 30 MHz transceiver. So the HG's from ICA are OK. ?????

all the schematics of that radio I see show just one final RF 2312. where can I see this version with 2 finals? I worked on the mosfet versions, very very similar. when You key down in AM, does the 6 V at the shorting board drop down when the RF output drops.?

" --- Just been trying to put it back to stock." Yes, that is what I like to do, back to stock, and adjust the AMC/ALC to maximum for good 100 percent modulation. And also get the RIT back to normal on all these radios..

"On pg 241 of Lou Franklin's book" - so what does he say about this capacitor?

This gave me something to do this morning while I drink some coffee. C154 (.047 mfd.) is a RF bypass capacitor at the emitter of TR37, which is the bias supply to the RF output final TR36. you can put anything in there from .001 to .1 mfd. or just leave it out. it is working now.

the reason resistor R128 was cut was to disable the microphone audio AMC/ALC circuit so that you can overmodulate. (on the mic on the left side version of this 148GTL radio)

I should add, do this first...... remove the "shorting board" to isolate the RF driver and output from this test. test the voltages at TP9. the 6 V or so in AM Mode, and 12 V in SSB mode.

Yes, I had this problem before. Months ago on a few of these types radios. just a "hunch" I have. sounds like maybe problem in the series amplitude modulator circuit. (Q66/Q67) SSB n FM will still work if a voltage reading is present. check the voltage at the "shorting board" TP7, 8, 9...

I was in Suriname July 4 maybe 1988 or so. city of Paranam. ? ?... at the ALCOA plant. (Aluminum Company of America) a civil war going on. Buses and cars on their sides, with bullet holes. we were at a bar. bullet holes in the walls. it was "Dutch Guiana" they spoke Dutch. I have...

I just downloaded the schematic. L14 would burn up due to high current through it. If one or more of the RF amp MOSFETS Q45/46/47 got destroyed, and a short from source to drain, this would cause this. also maybe burning up Q55 TIP36 and/or Q54 also? ? So first test at TP9 AM MOD. test...

that picture reminds me, on the JB2000 I worked on, one problem was them screws, star washers, and tube socket standoffs were not making a good contact with chassis ground. So took them all out, cleaned it up. put back together then had grounded-grid again.

Well, this website is viewed worldwide, so relatively speaking, I am down the bayou from you. On the Bayou near Thibodaux. And I am not originally from these parts of the country but been through Rayne quite a few times. Listened to KBON while out there. any progress on that board?

I replace these bad SMT transistors with good old style TO-92 devices. NPN - 2N3904, 2N2222. PNP - 2N3906. I leave long leads on them, and solder to the circuit board solder traces. Easy to bend the long leads to go in the correct place. (EBC) Hold the transistor with some tweezers, while...

Yes, a few months ago, I got one of these monsters to work. It had many hands in it. has a nice newer Dahl HV transformer. but all messed up. screwed up to the max!! found problems with the 8417 driver tube wiring. the resistor at the screen was incorrect. I took out the high/low switch...

the main radio schematic is "RCI 2950DX MOSFET" first check for the bias problem on the Q62. add that resistor is needed. on the 8 MOSFET PA board, turn the bias pots, VR2 and VR3 so the wiper is at ground, so you have zero bias voltage when first turned on. then monitor the input current...

also I found this error on the one I worked on. and the schematic confirms it, on the main circuit board. https://www.worldwidedx.com/threads/rci-2970n2-2950-irf520-bias-problem-repair.264585/