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Title: Collins R-390 Receiver RX problems Post by: WB4YVO on August 16, 2018, 11:27:01 PM All, Have been using this for many years It was working perfect yesterday. I turned it on today and NO Receive at all.. All bands The Calibrator doesn't work either.. So Receiver is completely deaf..It does make noise and all functions seem to work Just NO signals.. Antenna is Good it works on my other R-390A receiver..
Where do I start looking? What could happen as it sat overnight NOT On.. Its mounted in a rack with my R390A.. Its very heavy I will have to pull it and put on bench.. Help Any 390 experts out there?? Skip Title: Re: Collins R-390 Receiver RX problems Post by: KL7OF on August 17, 2018, 09:38:54 AM Start with the AC cord, then the fuse , then the switch on the front panel. ( before you pull the RX) Good Luck...Steve
Title: Re: Collins R-390 Receiver RX problems Post by: PA0NVD on August 17, 2018, 11:35:57 AM When it makes noise, the receiver including the IF seems ok. When it does not receive, my guess is that the oscillator for the first mixer doesn't work.
Title: Re: Collins R-390 Receiver RX problems Post by: KA3EKH on August 17, 2018, 01:26:49 PM The 3TF7 or whatever that stupid ballest tube is on the front of the IF amplifier section is always suspect. When that tube opens the there is no filament for the PTO and crystal oscillator deck so you get just what you describe. Noise but no signals. You can replace the tube with a resistor or zeniur diode although I forget the exact values. Don’t need filament regulation in normal use anyway.
Title: Re: Collins R-390 Receiver RX problems Post by: WD8KDG on August 17, 2018, 08:13:16 PM All, Have been using this for many years It was working perfect yesterday. I turned it on today and NO Receive at all.. All bands The Calibrator doesn't work either.. So Receiver is completely deaf..It does make noise and all functions seem to work Just NO signals.. Antenna is Good it works on my other R-390A receiver.. Where do I start looking? What could happen as it sat overnight NOT On.. Its mounted in a rack with my R390A.. Its very heavy I will have to pull it and put on bench.. Help Any 390 experts out there?? Skip Just to clarify...……..is the question pertaining to a R-390 or a R-390/A?? Regards, Craig Title: Re: Collins R-390 Receiver RX problems Post by: WB4YVO on August 17, 2018, 11:55:43 PM R-390
Skip Title: Re: Collins R-390 Receiver RX problems Post by: w3jn on August 18, 2018, 06:29:02 AM Either way, it's most likely the 3TF7. See if it's hot - if not, it's a gonner.
Easy workaround - replace the BFO and PTO tubes with 12BA6s and short across the appropriate pins of the 3TF7. The reason for the 3TF7 was to supposedly regulate the oscillator current. Great idea in 1951 taking into account possibly mobile environments on generators with fluctuating voltage - but completely unnecessary today. Title: Re: Collins R-390 Receiver RX problems Post by: WB4YVO on August 19, 2018, 11:40:55 AM OK, All Found problem My RF tube ( 6AJ5) was bad.. I did not have one so substituted a 6AK5.. radio now works again.. Will have to order some 6AJ5 tubes..
I was looking at the wrong tubes first in the IF chain.. Then realized I was not looking at the RF chain So first tube I replaced worked 1St RF Amp V201 Skip Title: Re: Collins R-390 Receiver RX problems Post by: PA0NVD on August 19, 2018, 05:10:46 PM 6AJ5 = 6F35
Fine that it works, the 6AK5 has twice the transconductance. Title: Re: Collins R-390 Receiver RX problems Post by: WB4YVO on August 19, 2018, 10:47:36 PM Well, I have ordered the right tube.. But at lease I know what the problem was..
Skip Title: Re: Collins R-390 Receiver RX problems Post by: WB4YVO on September 10, 2018, 09:30:11 PM Does anyone have a parts layout underside of the R390 IF Chassis? AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
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