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 Post subject: SP-600 Alignment problem
PostPosted: May Fri 11, 2018 1:25 am 
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Location: Livermore, CA
Started doing the alignment on the SP-600 and found that the receiver was deaf it could barely hear a 1-2uv signal, and 3 uv wasn't much better. After doing some resistance checks through out the receiver I found pin 5, V1 was open should be around 16.5K. So I pulled the RF deck out again and found L7 192 uh choke was open not sure how this happened, so now I have a 65lb door stop unless I can find a reasonable replacement. I found a 200uh choke at Mouser to try hopefully it will work. Since its just a plate choke how critical is the value of this choke?


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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Fri 11, 2018 1:59 am 
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Not critical. It is meant to isolate the plate from RF. Just be sure the current handling and voltage spec is sufficient. I worry about modern parts because many times they are for low voltage circuits. My 600 had one of those plate chokes broken, but still connected, so I just glued the break with Krazy glue and it worked fine.

Norm

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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Fri 11, 2018 3:11 am 
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I agree with Norm, its not critical and the mouser part should be OK.

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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Fri 11, 2018 4:19 am 
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Cool thanks guys have my fingers cross that's it with the problems.


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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Fri 11, 2018 2:50 pm 
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Anyone ever use a spectrum analyzer for alignment? It wouldn't be a modulated signal so I'm wondering how that might affect things?


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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Fri 11, 2018 5:31 pm 
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you might be able to tune it up just using the receiver's input noise, if you have a way of knowing exactly where your corner frequencies are, or you would need a tracking generator.

Another way would be to use a sweep generator and log detector, like I did here.

Image

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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Fri 11, 2018 11:14 pm 
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Mike,
After reading through some of the archived post about sweeping the I.F. I 'll just stick with the procedures in the manual doesn't really sound worth the effort.


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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Wed 16, 2018 3:42 pm 
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Update: I replaced the open RF choke with Mouser 807-1537-90J and I 'm glad to report all is good. After removing the RF deck for a second time to replace the RF choke I did a quick inspection of everything and reinstalled it. Upon power up there was a snap crackle pop sound, quickly turning off the power followed by a whiff of burnt component smell GREAT! no what?
So after waiting a day or so to cool down my temper the RF deck was removed for a third time. Inspection found one 33k resistor burned, and another looking a bit discolored I replaced the resistors, but there was still something wrong when measuring the resistance of the circuit. Using a magnifying glass I was able to find a blob of solder that was bridging between pins 5 and 4 V1, somehow when soldering the choke back in a blob of solder rolled off the back side of the tube socket pin and welded itself to pin 4 which is ground i.e. B+ to ground not good. Luckily the new choke was okay reinstalled the RF deck, applied power and the SP-600 came to life. Alignment went smooth everything went by the book the receiver is working real well I'm very pleased with its performance.


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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Wed 16, 2018 6:58 pm 
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Congratulations!

I always hate it when the problem is me - as it increasingly is. :roll:

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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Thu 17, 2018 3:01 pm 
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WoodchuckTN wrote:
Congratulations!

I always hate it when the problem is me - as it increasingly is. :roll:


Thanks
Yes me too must be an age thing.


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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Thu 17, 2018 5:21 pm 
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Quote:
Alignment went smooth everything went by the book


Glad this worked out for you. the alignment of my SP-600 stalled for a couple of reasons. Did you have problems aligning the higher frequency bands? (Every time I stick an alignment tool in there it seems to have a negative effect - even one I made out of an oak dowell).

Curious to hear - and what type of screwdriver did you use to get down into the turret?

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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Thu 17, 2018 9:11 pm 
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SmoothOscillator wrote:
Quote:
Alignment went smooth everything went by the book


Glad this worked out for you. the alignment of my SP-600 stalled for a couple of reasons. Did you have problems aligning the higher frequency bands? (Every time I stick an alignment tool in there it seems to have a negative effect - even one I made out of an oak dowell).

Curious to hear - and what type of screwdriver did you use to get down into the turret?


I used a hollow plastic alignment tool that has a small metal screw driver blade stuffed in the end of it. The tool is around 9" long, had no real problems accessing the turret adjustment points, but did need a flash light from time to time to see where I was aiming though. Yes the higher bands can be very tricky, when one finds the peak removal of the alignment tool causes the peak to move off frequency. So what I did was to find a point above or below the peak so when the tool was removed the peak moved back to the alignment frequency point this takes a few tries, and a few cuss words to get it right.

Dave


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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Thu 17, 2018 9:56 pm 
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Quote:
takes a few tries, and a few cuss words to get it right.


Great, thank you - that's helpful.

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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Thu 17, 2018 10:55 pm 
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Dave is quite right. If you shine a light into a hole other than the one you are working with, and look into a third hole, it makes it possible to easily see what you are aiming for with the alignment tool. It can be pretty frustrating otherwise. I have a small LED soldered on the end of two solid insulated #20 wires that I can fish into holes. A couple flashlight batteries completes the lighting device.

Norm


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 Post subject: Re: SP-600 Alignment problem
PostPosted: May Fri 18, 2018 3:24 am 
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Norm Johnson wrote:
Dave is quite right. If you shine a light into a hole other than the one you are working with, and look into a third hole, it makes it possible to easily see what you are aiming for with the alignment tool. It can be pretty frustrating otherwise. I have a small LED soldered on the end of two solid insulated #20 wires that I can fish into holes. A couple flashlight batteries completes the lighting device.

Norm

Good idea Norm I may try the LED trick you can get the light right down where one needs it.

Dave


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