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 Post subject: Royce 642 CB Base station or similar
PostPosted: Aug Fri 31, 2018 3:43 am 
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Joined: Mar Wed 22, 2017 9:56 pm
Posts: 12
I just pulled a late 1970's Royce 642 out of storage. I had kind of forgotten about it.
I got it working but weak on receive on usb and lsb and no receive on am. I would love to dig into it further but not without a better schematic and component location diagram. Something that showed voltages and waveforms would be nice like Sams Photofact.
Sams Photofact does not list this model. Sams does list the Pace 8193 which is supposed to be the same and is CB Radio Series 280. Sams 280 is out of print available at sams $22 for download and $34 reprinted, I have schematics for Royce 639 and SBE Land Command LCMS-4 which are similar (although mobile units} No componet location diagrams for them yet.
Just found the 40 pages for the Pace out of Sams CB Radio Series 280 on Ebay for $14.99 but the the seller is out of town till Sept 4 so no action on the purchase button.

"Description: Original Howard W. Sams & Co. INC. Photofact CB Radio Series service manual pages for the 1979 Pace model 8193."

What do you suppose this is an original CB-280 that has the pages cut out with a razor? I will try to buy it on Sept 4th if its still there.

So whats my question? Anybody else working on one of these base units? any idea where to get a real Royce 642 schematic?
Cheers
Band Reject


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 Post subject: Re: Royce 642 CB Base station or similar
PostPosted: Sep Sun 02, 2018 2:45 am 
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Joined: Nov Mon 05, 2012 10:05 am
Posts: 482
Location: Northwest Arkansas 72732
The Royce 642 owners manual has everything you need in it, and is specific for that model. There is at least one available now on ebay.


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 Post subject: Re: Royce 642 CB Base station or similar
PostPosted: Sep Sun 02, 2018 4:42 am 
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Joined: Jan Tue 23, 2007 10:23 pm
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Location: Chicago IL
Sounds like that radio is going to need an alignment. My advice for now would be to turn it on and keep it on for at least a week turning it on in the day and then off when you go to bed. This is what i call "cooking" the set. it will help all the circuits settle in before the alignment. Otherwise when you align it the settling will occur after alignment and everything will be out of whack again.

Beautiful radio.

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-Carlos


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 Post subject: Re: Royce 642 CB Base station or similar
PostPosted: Sep Sun 02, 2018 7:16 am 
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Joined: Mar Wed 22, 2017 9:56 pm
Posts: 12
Thanks for the replies

Quote:
The Royce 642 owners manual has everything you need in it, and is specific for that model.


I ordered the sams download. The Royce owners manual I saw on Ebay was kind of expensive and costly shipping from canada. It looks like the Sams will work. and worth the $22 to move forward with this project.
I like that is has componet locations.
Quote:
keep it on for at least a week turning it on in the day and then off when you go to bed.



Good advice I hadnt really thought of that. I did run it up on my isolation transformer slowly and ran it at about 60 percent the first several times I turned it on.

Now to dust of my old signal generator. I dont even know if it works. I might be buying a newer sig gen just to align this thing.
Original problem I found the collector of Q503 which is the driving transistor for the power supply pass transistor had a broken run right next to the pad where the lead is soldered to the circuit board.


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 Post subject: Re: Royce 642 CB Base station or similar
PostPosted: Sep Sun 02, 2018 9:01 am 
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Joined: May Sat 12, 2012 1:33 pm
Posts: 1690
Location: Rochester, NY.
Does the schematic give expected voltages at the transistors and test points? I would do some diagnosis before turning trimmer and coil adjustment screws.
Check solder joints and electrolytics.
Our local main library has the Sams Photofacts stored in file cabinets. If you ask for the specific folder, they will go to the backroom stacks and retrieve it for you. You can then photocopy what you need to take with you.


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 Post subject: Re: Royce 642 CB Base station or similar
PostPosted: Sep Sun 02, 2018 9:33 am 
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Location: Chicago IL
Wally58 wrote:
Does the schematic give expected voltages at the transistors and test points? I would do some diagnosis before turning trimmer and coil adjustment screws.



I would advice kind of the opposite. Usually going through an alignment procedure first is a sure fire way to weed out any issues the set may have. I wouldn't be surprised if this is the only issue with the set considering it's been stored away. Quite common. I recently started a CB club in my city and managed to get a few people on board, ever since I've worked on tons of equipment that had been stored away for decades. Most of it has been alignments.

bandreject wrote:
Now to dust of my old signal generator. I dont even know if it works. I might be buying a newer sig gen just to align this thing.


I would suggest you get a signal generator with a digital read out. The frequencies you will need to inject tend to be very precise and must not vary during alignment which is very easy to do with a old school vernier type generator. I don't know if you've aligned CB radios before, if you haven't, here are some must have pieces of equipment.

Signal Generator
Frequency Counter
Oscilloscope
RF Power meter.

The service manuals will often ask you for other pieces of equipment which you can work your way around not having but these are the most essential imo. None more essential than the frequency counter. In the past before I got my current test equipment I managed to perform alignments with only a vernier signal generator, frequency counter, and RF probe made out of an old stereo's VU meter. The radios I aligned with this set up I later checked up against my current test gear to find it was all dead on. :D

I could go on all day about all the tricky ways I've managed to do repair work with limited equipment. But ahh as time goes on and i gather more tools I'm starting to lose the knack and become spoiled by my equipment.

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-Carlos


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 Post subject: Re: Royce 642 CB Base station or similar
PostPosted: Sep Sun 02, 2018 1:55 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 154
Location: South Central Montana
Your Royce CB radio may suffer from poor connections in some of the many 'griplets' that connect the two sides of the circuit board traces together.

T.


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 Post subject: Re: Royce 642 CB Base station or similar
PostPosted: Sep Sun 02, 2018 3:16 pm 
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Joined: Mar Wed 22, 2017 9:56 pm
Posts: 12
Quote:
Does the schematic give expected voltages at the transistors and test points? I would do some diagnosis before turning trimmer and coil adjustment screws.
Check solder joints and electrolytics.


I havent really put it on a bench yet just preliminary diagnosis so far. I did suspect a capacitor 1000uf 16 volt cap at the collector of Q4 the first IF amp. Due to weak receive and the fact it looked like either leaking electrolytic or glue from where it was glued to the circuit board ( I couldn't tell) I pulled it and tested it for capacitance and then for ESR. I replaced it with a new cap as the ESR was not as good as a new cap but no change in symptom.

I did find that one bad solder joint in the power supply but nothing else obvious so far. It does have loud clear PA function which is kind of promising.

Quote:
Your Royce CB radio may suffer from poor connections in some of the many 'griplets' that connect the two sides of the circuit board traces together.


Funny I did not notice that Thanks I will look for them. That reminds me of the old GE Portacolor televisions which used to come in for service years ago. The first thing we would do is get the griplets hot and lots of rosin core solder just to get on level playing field with the little pieces of junk. Between that and the compactron tubes we used to call them porta junk. But in their defense they were the one of the first "portable" color sets available.

Quote:
Usually going through an alignment procedure first is a sure fire way to weed out any issues the set may have.


Agreed although If my curiosity gets the better of me I do veer off course at times and try something not very methodical.
Quote:
Signal Generator
Frequency Counter
Oscilloscope
RF Power meter.

Flying half blind here. I have a Software Scope (100Mhz) and a few RF power meters but I will likely have to buy a sig gen and I know I will have to buy a frequency counter. I wont buy the counter till I determine I need to work on xmit functions though. So far I have only noticed weak receive.

Cheers
Band Reject


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 Post subject: Re: Royce 642 CB Base station or similar
PostPosted: Sep Mon 03, 2018 3:47 am 
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Joined: Jan Tue 23, 2007 10:23 pm
Posts: 5375
Location: Chicago IL
bandreject wrote:
Flying half blind here. I have a Software Scope (100Mhz) and a few RF power meters but I will likely have to buy a sig gen and I know I will have to buy a frequency counter. I wont buy the counter till I determine I need to work on xmit functions though. So far I have only noticed weak receive.

Cheers
Band Reject


OOhh :D Sounds like my kinda project. Honestly if this is the case then I'd advice you again to get a frequency counter. Better to have that then the signal generator in this case. The receiver is where you need the signal generator and if you don't mind doing things a little on the "rustic" side then you can simply inject a signal using your existing generator and align all stages based off that and tweaking for overall gain. Is this the proper way to do it? No. Are the results pretty darn close to if you did it the right way, yes.

I don't use the alignment trick to weed out issues on everything, just communications gear as I've found it to be very efficient there. Also this is usually the way I go unless it's an issue I know can be solved through another trouble shooting method.

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-Carlos


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 Post subject: Re: Royce 642 CB Base station or similar
PostPosted: Sep Mon 03, 2018 2:20 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 743
Location: dayton oh usa
cbtricks does not have anything for that rig.
if its the one i think it is it is somewhat modular.
and plagued with bad through hole joints on its double sided board.
if so the first step is to locate and resolder every one of them from both sides.
expect lots of dried out caps too.
i remember replacing every one of the blue sanyo caps in older royce units.


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 Post subject: Re: Royce 642 CB Base station or similar
PostPosted: Sep Sun 16, 2018 3:55 am 
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Joined: Mar Wed 22, 2017 9:56 pm
Posts: 12
Since we have been discussing test equipment, I have tried to include some pictures. (Photobucket) Here is the Sig Gen lineup on the top shelf from left to right.
Leader LSG-16, Heath SG-8, B&W 200

[url][URL=http://s372.photobucket.com/user/langgatruck/media/Sig%20Gen%20Lineup%20800p_1.jpg.html]Image[/url][/url]

The Leader seems to work pretty well I have double checked it with a freq Counter LDC 823S which I bought on Ebay due to this project.A little trouble with the band selector switch which could use some DeOxit. The older sig gens need work.
You can see my new frequency counter barely in this picture with the blue LED display. How accurate is my counter? Gut feeling its ok but someday I will have to check against a known standard.


[url][URL=http://s372.photobucket.com/user/langgatruck/media/second%20pic%20in%20%20post_2.jpg.html]Image[/url][/url]

As I mentioned previously there is a no AM receive symptom on this radio as well as weak USB and LSB. After following the alignment procedure faithfully, which adjusted the power supply and set some frequencies on the Phase Lock Loop circuits finally I get to inject some modulated 9.8 Mhz on the base of Q5. I cant hear the 1Khz tone on AM but when I switch to USB or LSB I can hear it. The base of Q5 is right where the AM and sideband signals from the IF part ways. I suspected Q5 as the collector had expected voltage but emitter and base are at about 10 to 12 millivolts. Transister was pulled and checked front to back ratios with my Harbor Freight multimeter (I laugh but those little free red meters work for some things.) . I think the transistor is good.
with Q5 out, IC3 pin 3 still has negligible signal. P-P voltage is only about 30 to 50 milivolts.

[url][URL=http://s372.photobucket.com/user/langgatruck/m[URL=http://s372.photobucket.com/user/langgatruck/media/fourth%20pic%20in%20pose.jpg.html]Image[/url]edia/third%20pic%20in%20post.jpg.html]Image[/url][/url]

I have misdiagnosed IC's before and purchased them and it did not fix things. Still.
I found the IC for $12.00 shipped or 3 for $20 and ordered three. btw its actually an SL 1611C not whatever it shows in the picture or in the parts list.

[url][/url]

Here is the underside of the radio showing my Rigol software scope DS1052E which I am starting to like better. Just takes getting used to having a 1 or 2 second delay to see the results on the screen.

[url][URL=http://s372.photobucket.com/user/langgatruck/media/last%20pic%20in%20p%20ost.jpg.html]Image[/url][/url]


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 Post subject: Re: Royce 642 CB Base station or similar
PostPosted: Sep Mon 24, 2018 4:40 am 
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Joined: Mar Wed 22, 2017 9:56 pm
Posts: 12
I received the IC chip SL1611C Friday from an Ebay seller and got to work replacing IC 3 with the new part. after replacement I got the AM receive (noise) back with the replacement chip and was able to hear the 1khz tone from my sig generator pretty well and its louder now on Side bands. After about 5 minutes the replacement chip failed, and a lot of popping and static noise only. I had no choice but to put another IC in ( I had ordered three IC's).The second replacement IC seems to be holding and The AM receive is working again.

[url][URL=http://s372.photobucket.com/user/langgatruck/media/800%20pixel%20version%20closeup.jpg.html]Image[/url][/url]

Here in photo from left to right you see original, failed replacement part and the third untested replacement Ebay part.


With an antenna no radio signals but some strong pulsing noise. Keying the transmit switch does bring the xmit light on and receive shuts off but the transmit power meter is not showing any power out. The radio has strong clear PA audio so I plan to follow that audio starting where it modulates the transmit section.
I thought a little bit about strategy. First before more troubleshooting it is time to recap this 40 year old radio. I made a parts list with help of SAMs CB radio series parts list and the schematic. I already have in stock 12 of the new caps. I ordered 12 more values of electrolytic caps. That will be a complete replacement of all electrolytics. I guess I will replace about 6 caps at a time each time testing the radio for any changes.


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