Texas Star Black Widow - DX 350HDV Issue, Strange AM Watt Issue

[skiman1]

I just picked up a clean Toshiba loaded Texas Star Black Widow - DX 350HDV, and while SSB is perfect, the AM side has issues with AM carrier output. Even with my radio at 1 watt with the AM switch out, the carrier out from the amp is like 150+watts. With the AM switch in, its more manageable but still seems to be doing double what it should for the given input.

I have another 350 and my 148gtl was set up for it, and with 1.5 watts does 80w carrier out, swings around 300 PEP, with the Dial A Watt in and variable all the way up does 50'ish carrier out, swings 225 PEP. This Black Widow with the variable out does 150 carrier and around 300 PEP, variable engaged and all the way up does 100w carrier, swings around 300 PEP, and with the variable about 3'oclock, 50w carrier, 225 PEP.

I've given the amp a basic once over, nothing seems to be burned, unsoldered or damaged, but I see there's a trimmer cap that replaced C14, (see attached images) and I'm thinking it either came from the factory installed like this or someone installed it to tune the amp, thoughts?

Thanks, Skiman1

 

[nomadradio]

The newer the Texas Star amp, the more input attenuation they build in. Decade by decade as the average radio's transmit wattage more than doubled, they increased the loss factor in the amplifier's input circuit. A two-to-one difference in carrier from the old amplifier to the newer one isn't out of line. Consider that they both show the same peak output even though the transistors in one of them are being driven roughly twice as hard.

That's a hint that the additional drive level isn't accomplishing a lot, beyond "slicing off" the tops of your voice peaks. A radio half that size would probably sound better on the older amplifier. The AM button will accomplish roughly the same thing. Few radios are small enough to match the sensitivity of an old Texas Star with both AM and SSB buttons out.

73

 

[Handy Andy]

Well, congrats on getting a nearly pristine - or is it? - T/S amp selection.

Wanted to ask what are you using to measure these wattage values?

Noticed that the photos are showing several "differences" I normally don't see in a Texas Star, mostly the variables and the shield plate. That's new to me, although I've seen them in other amps and heated discussions in other forums - you may want to refer back to the buyer/maker of this set of amps - not sure if they need to be thanked for the preservation, but I do see more of their original design preserved - just several "tweaks" not usually found on their amps.

• But the one thing I do like to see is the effort to keep the original winds in the cores both of the input and outputs...
  
  • At least they're not adding/stuffing in more winds trying to re-match it for 26~30 MHz in an attempt to narrow down the bandwidth and increase the swing "capture" the radio is putting into the mess...
  • Many don't realize that by adding winds you also lose the conversion efficiency and admittance the transistors need to work correctly. It's not just bandwidth that is affected here.

So the previous owners/Builder took care, and consideration, for the users needs - especially low power.

So if you're experience with these is limited to "pinched up audio" and FM-ing, then you also need to think about what the former owner used with these amps. Things were supplanted into the amps to enhance them, nothing wrong with that. But their intricacy of the changes is what makes these stand out.

Their efforts in changes to the amp makes the amp personalized, it may be "more durable" in some ways, it does not mean the amp is bulletproof, just allowed to be stabilized using variables that have quirks of their own. Mostly that the variables reactions to temperature humidity and age is why they (OEM) installed FIXED values to get it consistent and out the door with fewer hassles as a "Drop in" to the system (the buyers) you're using it with. Doesn't mean it's tuned right, just this effort is a tuning done for a particular situation - not something you'd see direct from a Manufacturer.

 

[skiman1]

The newer the Texas Star amp, the more input attenuation they build in. Decade by decade as the average radio's transmit wattage more than doubled, they increased the loss factor in the amplifier's input circuit. A two-to-one difference in carrier from the old amplifier to the newer one isn't out of line. Consider that they both show the same peak output even though the transistors in one of them are being driven roughly twice as hard.

That's a hint that the additional drive level isn't accomplishing a lot, beyond "slicing off" the tops of your voice peaks. A radio half that size would probably sound better on the older amplifier. The AM button will accomplish roughly the same thing. Few radios are small enough to match the sensitivity of an old Texas Star with both AM and SSB buttons out.

73

That makes total sense, and probably why the current green Dial-A-Watt and Select-A-Watt buttons were once labeled "AM" with the Orange Button. It sounds perfect and nothing seems amiss so I think the mystery is solved, thank you!

 

[skiman1]

Well, congrats on getting a nearly pristine - or is it? - T/S amp selection.

Wanted to ask what are you using to measure these wattage values?

Noticed that the photos are showing several "differences" I normally don't see in a Texas Star, mostly the variables and the shield plate. That's new to me, although I've seen them in other amps and heated discussions in other forums - you may want to refer back to the buyer/maker of this set of amps - not sure if they need to be thanked for the preservation, but I do see more of their original design preserved - just several "tweaks" not usually found on their amps.

• But the one thing I do like to see is the effort to keep the original winds in the cores both of the input and outputs...
  
  • At least they're not adding/stuffing in more winds trying to re-match it for 26~30 MHz in an attempt to narrow down the bandwidth and increase the swing "capture" the radio is putting into the mess...
  • Many don't realize that by adding winds you also lose the conversion efficiency and admittance the transistors need to work correctly. It's not just bandwidth that is affected here.

So the previous owners/Builder took care, and consideration, for the users needs - especially low power.

So if you're experience with these is limited to "pinched up audio" and FM-ing, then you also need to think about what the former owner used with these amps. Things were supplanted into the amps to enhance them, nothing wrong with that. But their intricacy of the changes is what makes these stand out.

Their efforts in changes to the amp makes the amp personalized, it may be "more durable" in some ways, it does not mean the amp is bulletproof, just allowed to be stabilized using variables that have quirks of their own. Mostly that the variables reactions to temperature humidity and age is why they (OEM) installed FIXED values to get it consistent and out the door with fewer hassles as a "Drop in" to the system (the buyers) you're using it with. Doesn't mean it's tuned right, just this effort is a tuning done for a particular situation - not something you'd see direct from a Manufacturer.

Power readings using my MFJ-870, its spot on as it matches exactly the watts my Yaesu 991A is set to. Its actually in really nice shape, the only issue is the meter bulb is out and the meter cover is cracked, still works though, also a small ding in the corner of the cover where it must have been dropped at one point and how the meter got cracked. I remember having an older Texas Star amp years ago, was either this or a DX-400 and remember that same trimmer and shield plate, it also too had the Orange AM button instead of the Green Dial A Watt designation.