View Full Version : DRAKE 1A SSB TUNING
VE6HII
04-23-2010, 06:06 PM
Hello out there...Are there any fortunate souls out there who have a Drake 1A receiver(the first and breadbox) or who have worked on one who can give me some advice on fixing an upper sideband detection problem...//The rig works excellent on LSB CW and some AM but will not detect out USB signals..I have replaced the 6BY6converter and 12AU7 Product detector tubes to no avail...the rig is ssb only and the ssb control seems to work ok in the left lsb position but not in the right usb position..it will operate on cw but the range overall seems a bit wierd..Have adjusted the screw on the back of the ssb mechanism(mechanical attached to four slugs I believe in the ssb box..).which incidentally appears factory sealed(1958 I think)....there also doesnt appear to be any insertion adjustment or other usual ssb adjustments...Before I do something stupid, I'd thought I'd ask(I hate asking..like for directions..thx again...Bruce R 73 de VE6HII)...anyway, any help would be appreciated..otherwise its a lsb rig on 80 and 40..ps have the schematic but no repair manual(if there is such a thing...)...russellradio@jrtwave.com
It's been years since I had a Drake 1A, keep that in mind. My memory is pretty good but I have not downloaded a schematic.
The passband tuning in that is from the 50 kHz IF slugs being mechanically ganged to a movable plate. When you turn the passband knob, it shifts all the IF cans.
The BFO has to be centered in that passband range. In other words when the passband of the 50 kHz IF is shifted up, the BFO has to be just below it. When it is shifted down, the BFO has to be just above it.
Normally, even after 45 years, those slugs should NOT have changed. Contrary to what people think, things do not ever need alignment from age. If a component or components go bad it can shift the alignment, but the real cause of having to adjust all the screws is almost always because someone has adjusted screws.
Unless you understand how receiver systems work, I would ***NOT*** mess with the slugs on the 50 kHz IF or anything else. The very most you should try, unless you fully understand how the Drake IF system works, is to shift the 50 kHz BFO to the center of the passband.
If the 50 kHz IF has shifted off frequency, it could only be from two things...someone turn the screws, or a part went bad. If a part went bad and you turn the screws to "fix it", then the slugs will not track with each other and sensitivity and bandwidth will vary with the passband setting. If a cap went bad in the IF system it would have to be changed or tracking will fall apart.
73 Tom
VE6HII
04-24-2010, 07:42 PM
Hi Tom...Thanks for the sage advice...Fortunately I have not messed with the 4 slug aligment, but have gently tried to adjust the rear adjustable bolt that I believe adjusts the movement or travel of all 4 in sync, and basically the end result is somewhat improved detection but that is all...but I believe you are completly correct in that the 50 kc centre is out of whack or lowered somehow, allowing the ssb setting control range to operate only in the lower part of the passband ....I will give your suggestion a try...will have also the see if my signal generator will do the trick in that regard if necessary ...You are right about factory alignment..>That ssb "box" was sealed and soldered shut for a reason(HIHI)...anyway, I'll take it easy on the centring and report back...dont want to lose the lssb side which is fantastic for the old gem...73 de Bruce Russell VE6HII...ps you can see some of my toys on the QRZ site although the 1A I believe is outta sight...
Download a manual or download a schematic and post the schematic here. There should be a BFO coil that you can adjust. If things are not too out of whack that should give you LSB and USB.
Tom, shouldn't you be able to tell if the passband tuning is out of whack by listening to the pitch of the "white noise" coming out of the audio ? I would think that if it were OK, the noise would go from high, down to low, and then back to high again. Is it supposed to work that way ?
I am working on an R-599 that appears to have a crystal off frequency, and the symptoms it has are very similar. Real high pitch on USB and normal pitches on the other modes. If the 1A is not centered, that would be one of the symptoms, I would think!
Boy, the OP - what an unusual receiver! A real find !
VE6HII
04-25-2010, 03:33 AM
38360To W8JI...I'll try and post the schematic here once I figure out how to do it...compared to my computer skills , fixing the lsb problem is a piece of cake(HIHI)...73 de Bruce R.VE6HII38360
Big difference between computer repairs and boatanchor repairs has a lot to do with swapping out a board, vs. changing a single part !
Good luck!
VE6HII
04-25-2010, 11:07 PM
Hi Tom...Thanks for the sage advice...Fortunately I have not messed with the 4 slug aligment, but have gently tried to adjust the rear adjustable bolt that I believe adjusts the movement or travel of all 4 in sync, and basically the end result is somewhat improved detection but that is all...but I believe you are completly correct in that the 50 kc centre is out of whack or lowered somehow, allowing the ssb setting control range to operate only in the lower part of the passband ....I will give your suggestion a try...will have also the see if my signal generator will do the trick in that regard if necessary ...You are right about factory alignment..>That ssb "box" was sealed and soldered shut for a reason(HIHI)...anyway, I'll take it easy on the centring and report back...dont want to lose the lssb side which is fantastic for the old gem...73 de Bruce Russell VE6HII...ps you can see some of my toys on the QRZ site although the 1A I believe is outta sight...
Thanks everybody for the Help.....I DID IT>>>>LISTENING TO STOCKHOLM AND POLAND ON 20 METERS USB and PUERTO RICO on 40mlsb>>>>>>!!!What a job........!...never NEVER trust the factory setting of the SSB control knob...Left and right were totally off..had to sort of guess where it should be once I finished the job....2 the set screw on the back of the SSB Box had to be backed out considerably on USB to provide the dynamic difference to detect USB....3...then it was a question of setting off that setting with attempted centering for lsb on 40 m...4...then a combination of that saw off between usb and lsb with a similar saw off back and forth play with the 50 kc slug........VOILA......Stockholm on 20 and Puerto Rico on 40m.....and I can understand them...an excellent receiver..lots of fun learning from all of you as well... couldnt have done it without the suggesstions...Thanks again....73 de Bruce R. VE6HII
Thanks everybody for the Help.....I DID IT>>>>LISTENING TO STOCKHOLM AND POLAND ON 20 METERS USB and PUERTO RICO on 40mlsb>>>>>>!!!What a job........!...never NEVER trust the factory setting of the SSB control knob...Left and right were totally off..had to sort of guess where it should be once I finished the job....2 the set screw on the back of the SSB Box had to be backed out considerably on USB to provide the dynamic difference to detect USB....3...then it was a question of setting off that setting with attempted centering for lsb on 40 m...4...then a combination of that saw off between usb and lsb with a similar saw off back and forth play with the 50 kc slug........VOILA......Stockholm on 20 and Puerto Rico on 40m.....and I can understand them...an excellent receiver..lots of fun learning from all of you as well... couldnt have done it without the suggesstions...Thanks again....73 de Bruce R. VE6HII
Sorry I missed this for a few days and glad you "fixed" it. Be aware you could still have had a BFO problem and simply moved the IF range to match the BFO!!!!!
Yes, unequal pitch of "white noise" would be a sign something is wrong but it could be either all four IF transformers have shifted, or ONE BFO coil has shifted. That would be 12AU7's V5 and V10, or T6 and the few small components around T6.
It is statistically far more likely the BFO system shifted from a single component going off tolerance then the four coils right after V6.
BUT, moving the range of the four IF coils can easily make them match the BFO again. So it is possible you "fixed it" by moving the IF to a new frequency that matches the BFO.
It could have been the IF system shifted range, but I hope you follow why I would strongly suspect the BFO first. The BFO would have to be positioned in the very middle of the tuning range of the sealed IF unit to have both sidebands. It is statistically much more likely the BFO with a single much lower quality resonant components, and especially with it being an oscillator, shifted when compared with the multiple sealed, very good components, used by Drake for the selectivity section.
Either one shifting would have the same effect, so you could move the passband to "correct" either the four selective coils that by fate all moved at once in the same direction, or the single BFO coil, from moving.
T6 by itself (page 1 of the schematic) is the area I suspect being the actual problem simply because of the odds being much more likely a single coil-capacitor moved rather than four higher quality coils-capacitors moving all at once. Tube emission and type, for the V10 12AU7 tube, can cause the BFO to shift frequency a good bit too. Make sure that 12AU7 V10 is a 12AU7 and is good.
I'm pleased with my old brain. The schematic was about as I recalled from working on my 1A I had way back around 1967 or 68. :-)
73 Tom
VE6HII
04-27-2010, 10:16 PM
Sorry I missed this for a few days and glad you "fixed" it. Be aware you could still have had a BFO problem and simply moved the IF range to match the BFO!!!!!
Yes, unequal pitch of "white noise" would be a sign something is wrong but it could be either all four IF transformers have shifted, or ONE BFO coil has shifted. That would be 12AU7's V5 and V10, or T6 and the few small components around T6.
It is statistically far more likely the BFO system shifted from a single component going off tolerance then the four coils right after V6.
BUT, moving the range of the four IF coils can easily make them match the BFO again. So it is possible you "fixed it" by moving the IF to a new frequency that matches the BFO.
It could have been the IF system shifted range, but I hope you follow why I would strongly suspect the BFO first. The BFO would have to be positioned in the very middle of the tuning range of the sealed IF unit to have both sidebands. It is statistically much more likely the BFO with a single much lower quality resonant components, and especially with it being an oscillator, shifted when compared with the multiple sealed, very good components, used by Drake for the selectivity section.
Either one shifting would have the same effect, so you could move the passband to "correct" either the four selective coils that by fate all moved at once in the same direction, or the single BFO coil, from moving.
T6 by itself (page 1 of the schematic) is the area I suspect being the actual problem simply because of the odds being much more likely a single coil-capacitor moved rather than four higher quality coils-capacitors moving all at once. Tube emission and type, for the V10 12AU7 tube, can cause the BFO to shift frequency a good bit too. Make sure that 12AU7 V10 is a 12AU7 and is good.
I'm pleased with my old brain. The schematic was about as I recalled from working on my 1A I had way back around 1967 or 68. :-)
73 Tom
Hi Tom...Thanks again....A little knowledge is....(HIHI)...I am listening to the rig right now, it is still open and is working remarkably and will check the components as suggested...I belive the SSB can screw was only backed off about half a turn, so hopefully I wont break something that works fine while I am messing about ...I did replace V6 6BY6 the converter with a new high testing tube, likewise the 12AU7(V8) Product detector and the 12AU7 AF amp with new 12AU7As...I will recheck or replace V5 as per your note although it is a 6BQ7A(if I can find one)...I did check the resistances and voltages around the 12AU7 product detector and all were remarkably close to spec..I did not check or replace any of the caps to ground or coupling caps around the product detector or T5..I did notice the SSB knob is on a round 1/4 inch shaft and who knows if the original setting was factory or not but it did require some movement when I put it back on...Anyway, a real learning experience here and even if I fooled it into working , it sure is a remarkable radio..splits the sidebands perfectly as per the operating instructions...Thanks for all your help, and wow, what a memory without the schematic...73 de Bruce R. VE6HII
