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 Post subject: Sencore signal generator SG165
PostPosted: Feb Wed 14, 2018 12:12 am 
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I've been watching for a Sencore SG165 AM-FM signal generator, but haven't been quick enough to get one off the "Auction site". It seems that this has been the only place I've seen them come up. Looking at the responses to this unit have been mainly positive, so I'm interested when they show up. There is one on the big site, but unfortunately, it is local pickup only in San Diego. What a bummer!! It even has the original box! I know this one is unavailable for me, but just wondered if this model of signal generator is as good as it's cracked up to be. I won't be working on TV's , so I think this one has everything I would want. Anyone here have one, and if you do, do you like it? I'll keep searching. Currently I have a RCA WR-50B, but I haven't been able to use the sweep function on it with my scope. I have a Leader LBO 514A. I have a download of the WR 50B and get all of the correct waveforms from the unit (I believe), but can't seem to get the IF and FM detector waveforms when working on a radio.
I'm rather bummed.


Here's a link to the one on the "net" it's open until Sunday.

https://www.ebay.com/itm/sencore-SG165- ... SwkV5agJOl

Steve


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Wed 14, 2018 12:23 am 
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I have one. This might have the box but I don't see the probes with it, a big draw back..


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Wed 14, 2018 3:44 pm 
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Thanks for the reply Lou. I did download the manual for the Sencore a few years ago, at the time I didn't think the probes were going to be that hard to make, but I'll have to look again. It's really a moot point because there's a zero chance of getting this particular one. I would like to be able to do a proper FM alignment using a sweep generator, and the Sencore looked like a much better product than the RCA one I currently have (WR-50B). I have a couple of "test" radios I can do some more experimenting on to see if I can get the RCA unit working the way I want. The thing I liked about the Sencore was it had the FM multiplex, and audio output loads in addition to the standard IF alignment capabilities. I'll keep looking for one, but in the meantime I will have to do more investigating on why I am having issues with the RCA signal generator. Mainly I was looking to see how people that have the Sencore unit liked them, or if there was another unit out there that was similar.

Steve


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Wed 14, 2018 3:52 pm 
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Location: DFW Texas
Keep watching ebay and other sites. Go to ham meet if there is one near you.
several years ago I was at one and under a vendor's table was a piece of equipment with a $5 tag on it. At the time I had no clue what it was but even if it was dead it had enough meters and knobs to be worth $5. So I bought it and got it home. I powered it up and low and behold it worked. Googled it and downloaded a manual for it and found out that I had my very own Sencore SG165 and all functions work.

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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Wed 14, 2018 3:59 pm 
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Location: Tucson AZ
I have a SG-165 and it's a good generator. I had to build the probes for it and it wasn't difficult to do so don't let the lack of probes deter you.


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Wed 14, 2018 10:36 pm 
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See if they will take it to a ups place like postnet etc .....they willpack it per your iinstructions and you pay shipping....all the seller has to do is drop it off and send you the ups place phone no. There us a certain amount of trust required tho. Ive done thus a few times

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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Thu 15, 2018 4:08 am 
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Thanks for the replies, I wanted to know if getting this model signal generator would be worth it, and I take it as a "yes". I won't push my luck on this particular one, but will keep my eyes open. In the meantime, I'll do more research on why I'm having the issues with the current RCA generator. I've got plenty of time to practice.

Thanks,
Steve


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Thu 15, 2018 4:45 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Tucson AZ
42 people watching that one and I'd bet that the box with it drives the price up there, and the box isn't in that great of shape either.

They do seem to show up often there though, so you have to be quick if you see one at a good buy it now price.


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Thu 15, 2018 12:22 pm 
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They're a GOOD LITTLE GENERATOR, and it has all the signals needed to service consumer radios. I found one several years ago for ten bucks, it worked fine and I "Flipped"it on Ebay.

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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Thu 15, 2018 1:14 pm 
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To be perfectly honest, the SG-165 is nothing to rave about, despite what the internet "thinks," and I would not go out of my way for one. It is not a precision instrument. The main purpose was to take it outside and test car radios; that's why it has two audio wattmeters on it but the RF output is barely calibrated. The one thing it would give you that the WR-50B cannot is test signals for checking FM stereo multiplex decoders.

Quite frankly, if you are not getting good results with a WR-50B there is something about sweep procedure you're not doing correctly. Either you are not picking the detected signal off at the correct point or the scope sweep is not locked to the generator sweep, neither of which should be hard things to fix. The SG-165 does make the process simpler since it was built to drive a scope from the beginning, but you need to get it with the original probes or replicate them to take full advantage of its capabilities.

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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Thu 15, 2018 4:31 pm 
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Location: Tucson AZ
Chris108 wrote:
To be perfectly honest, the SG-165 is nothing to rave about, despite what the internet "thinks," and I would not go out of my way for one. It is not a precision instrument. The main purpose was to take it outside and test car radios; that's why it has two audio wattmeters on it but the RF output is barely calibrated. The one thing it would give you that the WR-50B cannot is test signals for checking FM stereo multiplex decoders.

Quite frankly, if you are not getting good results with a WR-50B there is something about sweep procedure you're not doing correctly. Either you are not picking the detected signal off at the correct point or the scope sweep is not locked to the generator sweep, neither of which should be hard things to fix. The SG-165 does make the process simpler since it was built to drive a scope from the beginning, but you need to get it with the original probes or replicate them to take full advantage of its capabilities.


Would you mind sharing your personal experiences with using a SG-165?


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Thu 15, 2018 4:56 pm 
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Joined: Jun Fri 19, 2009 6:34 pm
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Location: Long Island
Is there anything in particular you want to know? As a college student I worked part time in a professional radio and TV repair shop in the late 1970s and early 80s--I was young and flexible then so could get under car dashboards, so I got most of the auto radio work. The SG-165 was perfect for that because it was one small, lightweight box that did the work of two or three other instruments and you could prove channel separation and output power to the customer with it (this was way before the days of megawatt-power car audio shakers). It also worked very well on the bench for consumer radios, boom boxes and "back to college" quality stereo systems on the bench. But in terms of stability, accuracy, distortion, and leakage, it wasn't a contender for really serious hi-fi tuner and receiver testing.

The sweep function got used very rarely on most of these units, BTW, because from the mid 1970s on, most of the newer FM radios had crystal or ceramic filter IFs which are non-adjustable. The SG-165 does not sweep on the AM IF or RF frequencies.

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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Fri 16, 2018 12:08 am 
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Location: Saint Paul, Minn
Chris108, you bring up some valid points on that generator. While it is technology from the 70's, I was looking at it because it is somewhat an "All in 1" device. I like that aspect. I agree it probably won't be super accurate, but then I'm not starting a business and relying on equipment of this accuracy. What I would most likely be using this on would be radios and stereos older than that, I'm retired and this is only a hobby. In any case, you bring up a good point, I need to find out why I'm not getting the results I want using my current RCA WR-50B. If a Sencore unit comes up at a good price, I probably would purchase it, but until that time, I'm going to keep learning and use what I have. Like yourself, I was a technician in the late 70's, and was pretty good at it, but a change of job stopped all that. In fairness, I'm glad it turned out like it did, as I'm interested in repairing these old devices, and if I had been doing this all along, I probably wouldn't enjoy it now.

Lots of good feedback here, and I want to thank you all.

Respectfully,
Steve


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Wed 28, 2018 5:44 pm 
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Joined: Mar Sat 25, 2017 3:44 am
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I found my SG-165 on craigslist. Condition was listed as unknown but since it was cheep I got it. After a few parts were replaced it works fine. Taking time with the calibration procedures will yield fairly accurate outputs. Plus there are conversion charts in the manual.
As for the one the OP is/was watching on eBay, I cannot for the life of me understand what added value an original box would hold, but that's just me.
Another place to look/watch might be reverb.com HiFi related items often show up there. Good luck in your search and with some diligence you will find one.


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Feb Wed 28, 2018 6:58 pm 
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Joined: Jun Sun 23, 2013 9:03 pm
Posts: 392
Location: Canandaigua, NY
IMO, even if they work, most probably need some service to work right. Caps will often be bad and the thing is a nightmare to open and work on. It's also way bigger than you might expect if you haven't seen one in person. It's not a high precision device and wouldn't be your first choice for aligning higher end FM tuners. That said, it does a decent job and is the bee's knees for aligning traditional transformer tuned IF strips. That's my main use for it, having a small Leader mpx generator for tweaking THD. Some related threads:

http://audiokarma.org/forums/index.php? ... se.569018/
viewtopic.php?f=8&t=129016&start=40
I have some comparisons of THD here- http://audiokarma.org/forums/index.php? ... 466/page-2


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Mar Thu 01, 2018 1:42 am 
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Joined: Nov Thu 22, 2007 11:31 pm
Posts: 845
Location: Johnston, Iowa
Quote:
Is there anything in particular you want to know? As a college student I worked part time in a professional radio and TV repair shop in the late 1970s and early 80s--I was young and flexible then so could get under car dashboards, so I got most of the auto radio work. The SG-165 was perfect for that because it was one small, lightweight box that did the work of two or three other instruments and you could prove channel separation and output power to the customer with it (this was way before the days of megawatt-power car audio shakers). It also worked very well on the bench for consumer radios, boom boxes and "back to college" quality stereo systems on the bench. But in terms of stability, accuracy, distortion, and leakage, it wasn't a contender for really serious hi-fi tuner and receiver testing.


I wonder if that's why I've picked up two of them in the last 3 years at automotive swap meets. Both times I paid less that $25.00 for them.
Keith


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Mar Fri 02, 2018 11:27 pm 
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Location: Saint Paul, Minn
I was the original poster asking about the Sencore SG165

In the past week or so I decided to get a better scope than the one I had. Looking at many reviews I decided to go with a Tektronix 2235 100Mhz dual trace analog scope. Picked it up for a good price and tried an alignment with my current RCA WR-50B generator. This scope has a "line" source trigger and that made all the difference in the world. I can get the waveforms I had been expecting and not jumping around. The RCA generator syncs to the line frequency and now both pieces of equipment do. I have a 10.7 Mhz crystal that I put in the front of the generator and that will produce a marker at that frequency. I can now easily align the transformers to get the proper slope with the 10.7 marker in the center of the peak. What a difference! Although the generator is old school and probably not that accurate, the fact that I do have the 10.7 Mhz marker that is crystal controlled satisfies my accuracy requirement for the time being. I also have a 455Khz crystal for working on AM radios using 455Khz IF transformers. I do realize this setup would not be good enough for higher end tuners, but I have yet to work on one. My main hobby is stuff from the 50's and 60's AM-FM radios. I have worked on older AM only or AM-SW radios as vintage as 1931.

This hobby get more interesting all the time.

Steve


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Mar Tue 06, 2018 5:18 am 
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Joined: Jun Fri 26, 2009 2:27 am
Posts: 193
Location: Mississauga
Many top-end FM tuners require alignment adjusted to minimize distortion and the SG-165 has too much distortion to be usable for this but it is good for most other units.

For those of you rebuilding an SG-165, check the voltage at the source of TR-316. If it is low, you may be OK, but mine was at 6 volts (well within the MPF-102 spec) and that puts 18 volts across 400 ohms (counting R368). When I got mine, the output was clipped in the negative direction for the 400Hz output. The simple reason was R365 was a 1/2-watt resistor carrying 22.222 mA and dissipating 0.8666 watts. The 1/2 watt resistor had gone up to 2195 ohms. I put in a 1 watt resistor and it looked OK but was running too hot to touch, so I then added a 2 watt 390 ohm resistor and turned down the voltage balance on the power supply so I would get 12.1 volts on the positive output but 11.4 volts on the negative output. There is no reason to balance the power supply voltages - nothing depends on it.

I replaced the filter capacitors (input and output) in the power supply because the 15 volt rating on the 12 volt outputs means the reliability will be low, especially if the unit is turned on and the output voltage rises before the regulator has a chance to stabilize it. If I was going to be totally anal about it, I would change the rectifiers to fast recovery types as ordinary rectifiers tend to ring at 30 MHz and harmonics thereof and the third harmonic would be in-band for FM. A snubber capacitor may do the same thing, just less effectively.

I had to replace TR302 and TR316 because they were blown. I also added a 1.5 meg resistor to ground from the base of TR301 because I am not comfortable running transistors with a 15 volt Vceo with the base open when the resistor will bring it closer to the 30 volt Vcbo. I also replaced TR314 because it appeared to be shorted going by the diode voltage test on my DMM, but that was a mistake - it was actually seeing R358 and the removed transistor tested OK.

I can't complain about the SG-165 I got for $10 with these defects plus one channel of the audio meter was butchered - leads cut and not reconnected for some reason, but I never expect to use that function anyway. It was a piece of test equipment designed to a price to enable the average TV repair and stereo store to have AM - FM - FM MPX repair capability and it succeeded in that mission. I used PN3563 transistors for the oscillators, which are plastic versions of the SE-3002 transistors on the schematic and the 2N3563 transistors that were actually installed. The Vceo goes from the 12 volts of the SE-3002 to 15 volts on the PN3563 / 2N3563, critical in this circuit.

The unit is a royal pain to work on. It is built like a ship in a bottle and there is a delicate plastic shaft that has to be protected from breakage. If you fix the design faults, it is a good unit if you have limited space and must choose one unit for checkout of radio functionality.


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 Post subject: Re: Sencore signal generator SG165
PostPosted: Mar Tue 06, 2018 12:47 pm 
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Posts: 7943
Location: Long Island
Quote:
n the past week or so I decided to get a better scope than the one I had. Looking at many reviews I decided to go with a Tektronix 2235 100Mhz dual trace analog scope. Picked it up for a good price and tried an alignment with my current RCA WR-50B generator. This scope has a "line" source trigger and that made all the difference in the world. I can get the waveforms I had been expecting and not jumping around. The RCA generator syncs to the line frequency and now both pieces of equipment do. I have a 10.7 Mhz crystal that I put in the front of the generator and that will produce a marker at that frequency. I can now easily align the transformers to get the proper slope with the 10.7 marker in the center of the peak. What a difference! Although the generator is old school and probably not that accurate, the fact that I do have the 10.7 Mhz marker that is crystal controlled satisfies my accuracy requirement for the time being. I also have a 455Khz crystal for working on AM radios using 455Khz IF transformers. I do realize this setup would not be good enough for higher end tuners, but I have yet to work on one. My main hobby is stuff from the 50's and 60's AM-FM radios. I have worked on older AM only or AM-SW radios as vintage as 1931.


Glad you got the WR-50B working the way you want it to. The manual mentions using line lock on the scope but it is not intuitively obvious because there's no jack or control for it on the generator. (Some people bring the heater voltage from the generator out on binding posts for scopes which don't have a line lock feature). With the marker crystals it is about as accurate and functional as any sweep method can be. People tend to be dismissive of the WR-50B and WR-50C as they are "pint sized" lightweight instruments made by a consumer electronics company, but the folks who designed them knew exactly what they were doing. I would not try to set up a high end communications receiver with one, but dial accuracy and stability are good enough for just about any other vintage radios you will run across.

The matching RCA oscilloscope, the WO-33A, had line lock and included a phasing control so you could adjust the phase of the display when sweeping.

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 Post subject: Re: Sencore signal generator SG165
PostPosted: Mar Tue 06, 2018 3:43 pm 
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Location: Saint Paul, Minn
Chris108, the old scope I was using was a Leader 15 Mhz scope, a LBO-514A. It lacked any line frequency synchronization and that's why it was difficult to lock in a display. The new Tektronix is rock solid, plus a much clearer display and puts a whole new level of enjoyment on the hobby. Lots of new features than my old scope. Besides I paid less for the scope than any of the Sencore generators that were offered, and the last calibration that was done was in 2016. The new scope makes me want to purchase a radio just to fix it.
I just saw another SG165 on the auction site. I'm thinking it's one that just sold a little while ago and is being flipped. The prices they are getting for them is really going high now. I don't know what they sold for new, but I know I won't pay what they are asking. I like my little RCA unit.

Thanks everyone for all of your input. It helped me make a decision to purchase a better scope, rather than a Sencore SG165, and I know I made the right choice.

Steve


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