Texas Star DX350 - SSB delay causing loss in power output

[CbRadiosPRONTO]

35 Watt input SSB to Taxes Star DX350 @ 13.8v.

338 Watts Peak Envelope Power. Working perfectly. However, once the sideband delay is pressed on the amp, power is cut down 100 watts.

Similar issue w/ AM carrier. 3W input=140w out (seems high) When AM button is pressed, power drops. I just assumed it is a hi/low switch.

Who know what the issue is? I don’t often dink with amplifiers. Maybe it’s a bad/weak relay connection?



Video

Transmitting at 28.305MHz into 50ohm dummy load.

[edit] video was private ‍ now it should be working.

 

[999]

There is nothing wrong with the amplifier, it is functioning as designed. There is a power stage coupled with the delay on the standard amps.

 

[999]

This is the resistor in question.

 

[9C1Driver]

That's how they work. When you push the SSB button in the output is cut by like 30% er so. You need the 350 HDV variable model if you want full output in SSB mode.

 

[CbRadiosPRONTO]

That's how they work. When you push the SSB button in the output is cut by like 30% er so. You need the 350 HDV variable model if you want full output in SSB mode.

Hmm. Good to know. Thanks for the heads up.

 

[AudioShockwav]

Read through the thread below.

Older Texas Star D.C. 350 ssb delay

I have a question or three about the delay on my older dx 350. Amp info, older Bi-lateral 4 power (Texas Star) dx350. It does have 4 power levels, on AM, on ssb it has 2. Ssb power levels are the 2 lowest of the 4. My thoughts, I'd like to have a permanent/ automatic ssb delay. Thereby having...

www.worldwidedx.com

73
Jeff

 

[CbRadiosPRONTO]

Read through the thread below.

Older Texas Star D.C. 350 ssb delay

I have a question or three about the delay on my older dx 350. Amp info, older Bi-lateral 4 power (Texas Star) dx350. It does have 4 power levels, on AM, on ssb it has 2. Ssb power levels are the 2 lowest of the 4. My thoughts, I'd like to have a permanent/ automatic ssb delay. Thereby having...

www.worldwidedx.com

73
Jeff

Thanks, Jeff. The initial poster of

Read through the thread below.

Older Texas Star D.C. 350 ssb delay

I have a question or three about the delay on my older dx 350. Amp info, older Bi-lateral 4 power (Texas Star) dx350. It does have 4 power levels, on AM, on ssb it has 2. Ssb power levels are the 2 lowest of the 4. My thoughts, I'd like to have a permanent/ automatic ssb delay. Thereby having...

www.worldwidedx.com

73
Jeff

Thank you, Jeff. It sure is an awkward design. It appears I can simply bypass the ssb delay (and accompanied resistor) by adding a jumper between pin 2&3 on that gang. This will give me full power but also give me a delay at all times. I can install a toggle switch in the back to turn that on and off.

I don’t understand the purpose of this design but it appears I’m not the only one.

Thanks for the help. Unless otherwise suggested. Il will do this mañana.

 

[CbRadiosPRONTO]

There is nothing wrong with the amplifier, it is functioning as designed. There is a power stage coupled with the delay on the standard amps.

It appears I can jump pins 2&3 to get full power w/ ssb delay active. Will be trying that. Thanks for the help.

 

[Xracerx13]

I've done it to a couple texas stars. Works perfect with a switch mounted on the back panel wired to those pins in the red circle. Full power SSB with delay and no pushing in the button obviously.
The 4 power levels on AM are:
green & yellow buttons IN is LOWEST power output
yellow ONLY IN is next higher power
green ONLY IN is 3rd highest power
green & yellow OUT is HIGHEST power

 

[CbRadiosPRONTO]

I've done it to a couple texas stars. Works perfect with a switch mounted on the back panel wired to those pins in the red circle. Full power SSB with delay and no pushing in the button obviously.
The 4 power levels on AM are:
green & yellow buttons IN is LOWEST power output
yellow ONLY IN is next higher power
green ONLY IN is 3rd highest power
green & yellow OUT is HIGHEST power
View attachment 64562

Thanks, X. Consider it done.

 

[walterjn]

Thanks, Jeff. The initial poster of

Thank you, Jeff. It sure is an awkward design. It appears I can simply bypass the ssb delay (and accompanied resistor) by adding a jumper between pin 2&3 on that gang. This will give me full power but also give me a delay at all times. I can install a toggle switch in the back to turn that on and off.

I don’t understand the purpose of this design but it appears I’m not the only one.

Thanks for the help. Unless otherwise suggested. Il will do this mañana.

I wasn't happy with losing the full transmit power when I kicked into ssb. I never bothered to run a switch for the full power delay. I figure that if I need lower transmit power I can always push a button and reduce power that way. I really just wanted to be able to run WFO with the ssb delay.

 

[nomadradio]

Be sure and listen to it on another radio before and after.

The designer combined those two functions on the SSB button because sideband doesn't tolerate overdriving the transistors as well as AM mode does.

If you're okay with how it sounds, that's the opinion that matters, right? The drive gets reduced by that button to reduce flattopping. The peaks of your SSB RF envelope get clipped with full drive. The resistor reduces this effect by reducing drive level.

And a glance at this with a 'scope would confirm my suspicion, that peaks are getting flattened with the a jumper on that resistor.

73

 

[999]

Be sure and listen to it on another radio before and after.

The designer combined those two functions on the SSB button because sideband doesn't tolerate overdriving the transistors as well as AM mode does.

If you're okay with how it sounds, that's the opinion that matters, right? The drive gets reduced by that button to reduce flattopping. The peaks of your SSB RF envelope get clipped with full drive. The resistor reduces this effect by reducing drive level.

And a glance at this with a 'scope would confirm my suspicion, that peaks are getting flattened with the a jumper on that resistor.

73

Then why doesn't DX350HD drop the output power on SSB?

 

[nomadradio]

Either the factory changed the setup, or someone did after it was built.

Original schematics for Texas Star amplifiers, and for the last 40 years or so show the relay delay and drive-power cut combined in the sideband button switch.

And if they changed the way it's produced , I'll only hear about it this way. Don't see a lot of late-model Texas Star amps these days.

73

 

[999]

Either the factory changed the setup, or someone did after it was built.

Original schematics for Texas Star amplifiers, and for the last 40 years or so show the relay delay and drive-power cut combined in the sideband button switch.

And if they changed the way it's produced , I'll only hear about it this way. Don't see a lot of late-model Texas Star amps these days.

73

This is the schematic for the HDV 250 and 350. Note that the switch (mounted on the rear of the cabinet) only controls the delay cap with no power level setting. This is how they manufactured the HDV 2 transistor amps for decades.