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 Post subject: Collins R-390 alignment
PostPosted: Oct Tue 09, 2018 4:31 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 19126
Location: Warner Robins, GA
Been noticing for the last month or so that my R-390 was not as sensitive as it should be to where my RCA K-80 console was a good bit more sensitive than the receiver.

I thought well it needs an alignment since I was unsure of the previous alignment I did knowing the way I did it wasn't exactly kosher far as the RF generator is concerned.

Got prepared for the alignment and noticed a tuning slug (third rack from the right and rear slug) had fell out of the adjustment screw. So I carefully removed the rack and pushed it back in properly. I then gave a slight tug and it wasn't moving back out. So I reinstalled the rack and verified operation.

It was better, but while I had it apart I figured I'll touch up the alignment.

I used the same Stark RF generator as before only this time I had the digital frequency display properly mounted and working as it should to where it accurately indicated the frequency and the vernier drive is perfected so I have fine frequency control.

I proceeded to do the alignment and the IF was off a bit so I fixed that. The RF wasn't off as bad. The XTAL oscillator was off as well.

After doing that I had to adjust the BFO.

The receiver itself now seems to perform much better.

I do have a question.

I noticed that earlier this evening I could pick up WWV on either 10 or 15MHz quite decently.

Later on I noticed a lot of static that actually registered around 30 on the carrier meter and it went away when I unplugged the antenna. Seemed to be like that on most of the shortwave at at least 5-15MHz only changing the MHZ control.

Is that some sort of local interference or is that some sort of problem affecting all shortwave?

Also if I got a proper RF generator could the alignment be improved any further? Seems to be the best it can be now with my setup.


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 Post subject: Re: Collins R-390 alignment
PostPosted: Oct Tue 09, 2018 5:39 am 
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Joined: Sep Thu 01, 2016 3:56 am
Posts: 214
Location: San Jose, Ca.
In the 390's and other good receivers, noise usually does not come in through the power connection or the internal circuitry like the rf amp etc, as they are usually shielded for that. But locally generated noise can and does come in through the antenna. I'm in San Jose and just listened to 5-15 mh and do not detect unusually high 'band' noise at this time, but that's here and not there. I can pickup 10 and 15 MH WWV right now. Sometimes locally generated noise is hard to distinguish from band noise, for instance if you have a high voltage power line insulator that is leaking. Try looking at it with a scope. Others are easy to identify and track down with a portable radio with a directional antenna.

My guess is that it is locally generated, because of the strength. The best way to keep local noise out of your rx is to use well grounded coax at the rx (using the balanced input), not the antenna end.

A properly aligned 390 will pickup less noise than one that is not. For proper alignment, an accurate sig gen is not required, but it does need to be fairly well shielded. On 390's, it's important that all alignment adjustments peak at other than the ends of travel. And that the vfo end point is not very far off from 1 MH.

Hope you find it.

Regards, Larry


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 Post subject: Re: Collins R-390 alignment
PostPosted: Oct Tue 09, 2018 12:09 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 19126
Location: Warner Robins, GA
I know the VFO is slightly off at certain points, but everything seemed to peak up properly. I know what the fix to that is, but I'm dreading having to do it as it isn't an easy procedure from what I could tell.

Not sure it's local noise unless it's something that just started recently at night only. I do know the noise was there before I aligned it.

Perhaps this could explain the noise I heard which was staticky type noise, but it wasn't an interference type of noise.

https://dx.qsl.net/propagation/

Earlier in the afternoon I heard none of that type of noise or at least it wasn't nearly as bad and was pretty much like the typical static between stations.


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 Post subject: Re: Collins R-390 alignment
PostPosted: Oct Tue 09, 2018 1:57 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 5645
Any cheap shortwave portable can pretty quickly be used to tell whether it is local noise, something coming in via an antenna, or a receiver problem. From your description it was probably locally generated noise that could be anything from the common switching power supply noise to wind induced static buildup on your antenna (depending upon antenna type and connection). One of the low cost Chinese sourced shortwave portables is a cheap purchase, is useful on the test bench, provides a quick test of suspected failures of another receiver, and is extremely useful in running down local noise sources. One of my Grundig YB-400 receivers spends all of its time on the test bench and comes in very handy but I have also used it to run down the source of noise on the home wiring (switching wall warts, Nintendo PS, extremely noisy CFL, etc.).

Rodger WQ9E


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 Post subject: Re: Collins R-390 alignment
PostPosted: Oct Tue 09, 2018 2:58 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 19126
Location: Warner Robins, GA
I can check that, but the antenna is indoors and previously until a few days ago did not have that noise at night.

Pretty much everything that uses a switching power supply is on both during the day and night.

I do know the plate amp for a powered sub I have in the room causes RFI on the AM band so I turn it off when using the receiver.


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 Post subject: Re: Collins R-390 alignment
PostPosted: Oct Wed 10, 2018 2:05 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 19126
Location: Warner Robins, GA
Reception seemed to be much better tonight.

The static tonight seemed to be more of a normal between station static.

Not quite sure what it was that gave me such a problem yesterday.

The only thing I did not do was check the overall RF gain and adjust the gain pot as I don't have a good enough signal generator to do that.

EDIT:

Found something quite interesting.

Was having trouble picking up 700 WLW with my indoor antenna which is around the room on the wall 2" from the ceiling so I tried my external antenna which is mounted below the back porch and it picks up WLW much better with less static.

I then tried 1350 which is a local station and it picks up better on the internal antenna. Same with 940 which is a local although the difference is not as great as it is at 1350 and 700.

What's odd is the same type of indoor antenna in my 12' X 12' building and nearly the same length (think it is but the one in the house could be slightly shorter) worked so well with the R-390 and my SP-600 JX-17.

Not sure what's going on as the indoor antenna seemed to work better than the external antenna at one point.

Now could the alignment being off make one antenna work better than the other? If so perhaps that explains why the indoor antenna worked so well.

Was hoping my dad would cover the back porch so I would have a place to run an antenna wire high up for best reception. If I ever get that done I'm thinking of running coax from the R-390 and connecting it to the antenna so that it is not affected by anything between the R-390 and the outside. I'll then run a second wire for my RCA K-80 console.

Thinking about it I suspect the hurricane might be causing some of my reception problems as on the internal and external antennas I could not get Radio Havana Cuba on 6MHz and it usually is fairly strong here once being able to pick it up loud and clear with only a 3" piece of wire in the antenna jack of my SP-600.

What's odd is my Philco 118 receives 940 quite good with maybe a 10' antenna.

Now with the R-390 I did a mod to do away with the transformer that drives the audio filters.

That also removed the cap that was between the transformer primary and ground. Could it be that the upper audio frequencies aren't being cut enough which would make the static more obnoxous?


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 Post subject: Re: Collins R-390 alignment
PostPosted: Oct Wed 10, 2018 5:50 am 
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Joined: Sep Thu 01, 2016 3:56 am
Posts: 214
Location: San Jose, Ca.
The alignment on the 390 could cause more noise rejection when properly aligned. This is due to a narrower band pass.

Antenna position and orientation can make a difference. Lot's of other factors, too.

Removing that audio transformer will probably let more audio highs through, which normally emphasizes noise.

Regards, Larry


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 Post subject: Re: Collins R-390 alignment
PostPosted: Oct Wed 10, 2018 11:34 am 
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Location: Warner Robins, GA
The alignment seems fine from what I can tell at least the IF alignment is ok.

I know the PTO is slightly off such that for best reception of 940 I have to be at 944.

I need to read up on how to adjust that. Once properly adjusted I will go back through the RF alignment.

Agreed about the audio transformer being gone allowing more highs through. I tried the original capacitor from plate to ground of the 12AU7 that originally drove the transformer as I had used a 10K plate resistor and cap coupled it to a 25L6 cathode follower stage and when I added the cap the stage turned into an oscillator. I did not try the cap across the 10K resistor so maybe I'll try that.

It does seem like the audio from the line audio out jack (use that to feed my stereo and it has its transformer installed) doesn't have as much highs though.

I did remove a tweeter I had used to tame the upper midrange/lower treble, but when I was receiving my two tube broadcaster it sounded fine. Perhaps I need to add that back, although the bass seems to sound better without the grill the tweeter was mounted to in place given the grill was directly in front of the speaker between it and the cabinet.


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 Post subject: Re: Collins R-390 alignment
PostPosted: Oct Thu 11, 2018 5:36 am 
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Joined: Mar Fri 29, 2013 4:46 am
Posts: 172
Location: Livermore, CA
Tube Radio wrote:
The alignment seems fine from what I can tell at least the IF alignment is ok.

I know the PTO is slightly off such that for best reception of 940 I have to be at 944.

I need to read up on how to adjust that. Once properly adjusted I will go back through the RF alignment.



The end point adjustment is not too hard to do I have the Cosmos PTO in my 390a the end point was way off I finally had to remove one turn on the end point adjustment inductor inside the PTO itself. I probably spent 45 min to an hour getting mine adjusted its now tits on sure is nice having the PTO track correctly. http://www.r-390.com/pto.htm
So far I've done 3 alignments each time it seems to get just a little bit better, also been thinking of Chuck Rippel's R390a CD's, but $140.00 seems a little steep to me.
If you havn't already seen this site https://www.radioblvd.com/R-390A%20Rebuild.htm please do Henry is a walking encyclopedia, and a real nice person as well I talk with him almost weekly he's helped me through a few 390a issues I've had in the past.


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 Post subject: Re: Collins R-390 alignment
PostPosted: Oct Thu 11, 2018 4:14 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 19126
Location: Warner Robins, GA
Thanks for that.

I'll give it a try this weekend


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