Regency Range Gain low modulation

[guitar_199]

Tramd, just an update from my direction.....

Certain parts of the Range Gain schematic look VERY different as you have already said.

On a lark.... I went to look at the Range Gain II SAMS (CB-13) schematic and "guess what"? It matches what Champo sees in his actual radio. The main area I am talking about are the MicAmp/Squelch amp tube. The CB-5 schematic has the two halves REVERSED from the factory manual schematic. Very oddly.... the CB-13 (Range Gain II, CB-13) has them correct!

Additionally in the area around V2... while parts are the same.... voltage readings are different from the CB-5 schematic... AND THEY MORE CLOSELY MATCH what Champo is seeing in his radio.

Not saying CB-13/Range Gain II is the RIGHT schematic....but I thihnk we are going to "add it in to the fold" as an additional resource as we go through this.

And, yet another thing.... even though the oscillator circuits are near identical.... the TX alignment procedure looks to be more straightforward. More of a "Tune for MAX" concept and does not require a sweep generator.

This really is an adventure!!!!!!

Bob

One thing about SAMS is that they usually rewrote the schematics and renamed everything so it becomes confusing when one tries to compare them to the original. Once you understand that and know what you're looking at it's not a problem. They can actually be easier to read than some originals. Since they are rewritten there are mistakes sometimes but you will come across mistakes in originals as well. Also SAMS usually rewrote the alignment procedures too. Another thing is that many radio manufacturers made updates to their radios. They most likely printed revised schematics but most never released them. So there may be differences from the radio you are working on as compared to the schematics that they released. The problem then is what revision radio do you actually have? Tram D201As are like that. There were many revisions but only one schematic released. I once had three TRC 458 Navahos that were built within 2 years (1977-1978) that had different cap arrangements on the bottom side of the board but only one schematic was released. GE Superbases and like radios come to mind with their three versions as well as many other radios. Another problem with SAMS is that usually you don't know what revision they wrote their schematics from. If only one was released that is probably what they used. If many were released such as in the case of the Tram Titan II, the one SAMS used was most likely the current one at the time. The one they used for the Titan II was R2 but there was also R3 and R4 later on due to improvements that were made to the radio.

 

[Dmans]

guitar_199,
Quite a discovery! Hats off to you!

73
David

 

[guitar_199]

Well..... I'll hold off on celebrating till I see where Champo gets with this alignment.

I can attest that the SAME STRIP OF COILS.....gets a totally different alignment procedure....even though the circuit looks to be the same. ON the Range Gain they are tuned during the receive alignment. On the Range Gain II they are aligned during the transmit alignment.

Weird.....but.... here we sit.

 

[Champo]

Tramd, just an update from my direction.....

Certain parts of the Range Gain schematic look VERY different as you have already said.

On a lark.... I went to look at the Range Gain II SAMS (CB-13) schematic and "guess what"? It matches what Champo sees in his actual radio. The main area I am talking about are the MicAmp/Squelch amp tube. The CB-5 schematic has the two halves REVERSED from the factory manual schematic. Very oddly.... the CB-13 (Range Gain II, CB-13) has them correct!

Additionally in the area around V2... while parts are the same.... voltage readings are different from the CB-5 schematic... AND THEY MORE CLOSELY MATCH what Champo is seeing in his radio.

Not saying CB-13/Range Gain II is the RIGHT schematic....but I thihnk we are going to "add it in to the fold" as an additional resource as we go through this.

And, yet another thing.... even though the oscillator circuits are near identical.... the TX alignment procedure looks to be more straightforward. More of a "Tune for MAX" concept and does not require a sweep generator.

This really is an adventure!!!!!!

Bob

I want to thank everyone for their help! Without it I'd have a very nice looking paper weight...or boat anchor lol!

Tramd, just an update from my direction.....

Certain parts of the Range Gain schematic look VERY different as you have already said.

On a lark.... I went to look at the Range Gain II SAMS (CB-13) schematic and "guess what"? It matches what Champo sees in his actual radio. The main area I am talking about are the MicAmp/Squelch amp tube. The CB-5 schematic has the two halves REVERSED from the factory manual schematic. Very oddly.... the CB-13 (Range Gain II, CB-13) has them correct!

Additionally in the area around V2... while parts are the same.... voltage readings are different from the CB-5 schematic... AND THEY MORE CLOSELY MATCH what Champo is seeing in his radio.

Not saying CB-13/Range Gain II is the RIGHT schematic....but I thihnk we are going to "add it in to the fold" as an additional resource as we go through this.

And, yet another thing.... even though the oscillator circuits are near identical.... the TX alignment procedure looks to be more straightforward. More of a "Tune for MAX" concept and does not require a sweep generator.

This really is an adventure!!!!!!

Bob

Yes the Range Gain II alignment instructions are definitely the way to go. As soon as I get a minute I'll get to it. Thank you for the info guitar_199!

 

[Champo]

Dmans if you have any recommendations regarding the VNA I'd love to hear them. I have one arriving later this week.

 

[Champo]

Well no luck with the tuning. I ran through the tuning process as discussed and and can get no better than .5-.75 watt deadkey swinging to 1.5 watts. I've also tried 2 new 6AQ5's, 2 6AN8's and 3 different 12BH7 tubes with no more than the above output. I'm at a loss as to what to do next. I'm hoping the VNA will prove helpful because I'm pretty much out of options

 

[Dmans]

recommendations regarding the VNA

Champo,
You will probably need a pair of SMA to small alligator clip leads to use the VNA to align the IF coils. Check Youtube. There are plenty of videos explaining the process.

73
David

 

[nomadradio]

Hmm. Betcha it's full of "K-Tran"s.

Not a good sign.

73

 

[Champo]

Hmm. Betcha it's full of "K-Tran"s.

Not a good sign.

73

Please explain

 

[Champo]

Please explain

I think I've connected the dots...IF transformers. It does look like that's what is in there. What's the "known" problem with them? I think I stumbled across this issue in a post about an Olsen Sidebander and I just became aware that they're the same @#$^ing radio! FML! I think the plastic becomes brittle over time if I recall. Correct me if I'm wrong. Is there a fix or am I screwed? Was the failure the result of environment i.e. heat or just the material was garbage? I'm into this radio for a pretty penny at this point with a PAL VFO on the way so fingers crossed you have a lifeline for me Nomad! I can pick up 4 NOS IF transformers for $20 and salvage my investment if it's just a result of the environment taking its toll on them i.e. they're not friendly in that hot environment. I could then run them until they die. Cooling fans may extend that life a tad. If it was just manufacturing then I might be screwed. Let me know your thoughts! The FT-101E is still running well by the way! Thanks for the help on that!

 

[nomadradio]

The K-Tran was a high-tech IF transformer in the 1950s. It is designed first to shield the magnetic field inside the can, so you can put them close alongside one another inside the radio. This is done with a so-called "cup" core of ferrite that surrounds the coil inside. Older IF transformers had to be spaced farther apart to prevent magnetic coupling between adjacent transformers.

The internal frame is made from clear polystyrene. A plastic that shrinks and becomes brittle with age and exposure to heat.

The fatal flaw is the internal capacitors. To make each coil inside tune the proper frequency a capacitor is built in the bottom of the can. It's made from alternating layers of metal and mica sheet. A 'V'-shaped steel spring presses the layers tightly together. A brass rivet at the bottom is what holds the steel spring against the stack of capacitor layers.

It's a genuine high-performance component. The plastic frame has a very low RF loss, the stacked-plate capacitors in the bottom have a lot of surface area, making the capacitor's internal resistance low. This increases the "Q", or selectivity of the tuned circuits inside.

Until age catches up with the polystyrene plastic. As it shrinks the stacks of capacitor plates begin to separate. The loss of tension pressing them together becomes a random on again/off again problem as small temperature changes cause the parts to shift around against one another.

Simply replacing those internal capacitors should fix the problem, right?

Easier said than done. Not totally impossible, but labor intensive. And if that brittle plastic frame comes apart while removing the brass rivet, it's Humpty-Dumpty time.

No easy answers to this dilemma.

73

 

[Champo]

The K-Tran was a high-tech IF transformer in the 1950s. It is designed first to shield the magnetic field inside the can, so you can put them close alongside one another inside the radio. This is done with a so-called "cup" core of ferrite that surrounds the coil inside. Older IF transformers had to be spaced farther apart to prevent magnetic coupling between adjacent transformers.

The internal frame is made from clear polystyrene. A plastic that shrinks and becomes brittle with age and exposure to heat.

The fatal flaw is the internal capacitors. To make each coil inside tune the proper frequency a capacitor is built in the bottom of the can. It's made from alternating layers of metal and mica sheet. A 'V'-shaped steel spring presses the layers tightly together. A brass rivet at the bottom is what holds the steel spring against the stack of capacitor layers.

It's a genuine high-performance component. The plastic frame has a very low RF loss, the stacked-plate capacitors in the bottom have a lot of surface area, making the capacitor's internal resistance low. This increases the "Q", or selectivity of the tuned circuits inside.

Until age catches up with the polystyrene plastic. As it shrinks the stacks of capacitor plates begin to separate. The loss of tension pressing them together becomes a random on again/off again problem as small temperature changes cause the parts to shift around against one another.

Simply replacing those internal capacitors should fix the problem, right?

Easier said than done. Not totally impossible, but labor intensive. And if that brittle plastic frame comes apart while removing the brass rivet, it's Humpty-Dumpty time.

No easy answers to this dilemma.

73

I can't do anything about the age aspect but what are your thoughts regarding NOS K-Trans IF transformers. Having not been exposed to heat what do you think the likelihood of success would be in regards to replacement? A temporary bandaid of sorts?

Also please excuse my ignorance regarding the next question. They all appear to be in the receive strip but did they also play a role in transmit?

Thanks for your help and thorough explanation!

https://www.ebay.com/itm/2-VINTAGE-...2349624.m46890.l49286&mkrid=711-127632-2357-0

 

[Champo]

@nomadradio What are your thoughts on the placement of the the K-Trans cans and their interaction with transmit? I could really use some help. No luck with new 7.5MC crystals (though the frequency is tight and on point now) and a follow up alignment. I'm still getting positive voltage at the grid during transmit when it should be going negative. Thanks!

 

[Champo]

Just to add. @guitar_199 requested that I compare values to a working Sonar FS-23 that I have. It follows the same pattern as the Regency where the grid goes negative during transmit. Here are the results:

"Interesting note on the Sonar. Pin 2 of V13 (final amp 6BQ5) on the final tube is -.17vdc and when keyed it drops to -.87vdc but not to the -8.6vdc that the Sam's calls out. I wonder if that is a simple decimal point error in the Sam's or a coincidence? It starts off at 0 but slowly ticks down to -.17vdc. After unkeying it will start out at 0 and slowly tick down (-.01, -.02, -.03 etc) until it bottoms out at -.17vdc.

Pin 1 of V12 (buffer amp 6AU6) follows a similar pattern. It starts off at 0 but slowly ticks down to -.45vdc and increases to -.40vdc but doesn't drop to the -3.8vdc the Sam's calls out. Again really close values (-3.8, -.40) if you move the decimal point. If you key up before it maxes out, say at -.17vdc it'll drop to the -.40vdc.

Nonetheless, the values are still negative whereas with the Regency they never go negative even to a minute degree."

Jacob

 

[Champo]

I just wanted to post a quick update about where I am at the moment. Guitar_199 hooked me up with some instructions on how to build an rf sniffer and how to use it with the VNA to check the oscillators. I was also able to max their output or align their output across all 23 channels. As it stands I'm getting the correct mixed frequencies from the first two oscillators all the way to the third oscillator (V11). I am not getting the 7.5mhz crystal mixing with the other two signals to give me a frequency in the 11 meter band though. The 7.5mhz crystal shows that it is at 7.255mhz when installed however when the crystal is removed it tests correctly at 7.5mhz. The original crystal, which was working prior to all output dieing and was on frequency per a frequency counter confirmationas well as an on air radio check, also presents the exact same way. So, what would prevent the 7.5mhz crystal from mixing with the first 2 frequencies and also why would the crystal show that it is low when installed? I also checked frequencies as if it were indeed off by 245khz but still nothing registered on the VNA. I also tried a second tube at V11 with the same results. Thanks!