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Texas star DX500

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295 antenna
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Texas star DX500

Post by 295 antenna » Wednesday, 14 February 2018, 14:41 PM

Well i knew she would go some day but my 36 or so yrs Amp finally failed. i saw my output drop to half and my swr sky rocketed. No time today but stay tuned when i open it up and take a look around. Maybe it an easy fix ?
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Re: Texas star DX500

Post by Blue Ox2 » Thursday, 15 February 2018, 1:46 AM

Good luck with that Charles.

I am sure you will find the issue and have it corrected
in no time.

73 pal,

Mike

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Re: Texas star DX500

Post by sonoma » Thursday, 15 February 2018, 2:31 AM

295 I have a trouble shooting chart wrote up by a texas star amp builder that I can send you if you will PM me your email address. he use to have a web site and has since passed away from what I have heard.. I will send it to you for help to diagnose your problem

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Re: Texas star DX500

Post by sonoma » Thursday, 15 February 2018, 4:22 AM

lets see if I can just copy and paste some of the info.

Troubleshooting:
First we need to really determine exactly what is wrong.
I will describe some common conditions and go from there.
No receive:
when the power is on, does the light behind the meter turn on?
if the meter light turns on without being keyed up, then the keying transistor is
shorted. Remove the 2n2907a which is located behind the relay.
now the lamp should not turn on.
if the meter lamp does not turn on and there is not receive, I expect that the receive
transistor is not working. Replace the transistor behind the receive switch.
Use a 2907a
No transmit output:
let's back up and start from scratch.
Turn the amp off. Key the radio. The radio should pass radio
power straight through it and should have a low SWR. If the
straight through condition is not A-OK, we need to fix that before
we do anything else.
Turn on amp and key up radio. Does the relay click? Does the
meter lamp light up while radio is keyed up?
If the relay doesn't click and meter lamp turn on, replace the
keying transistor with a new 2n2907a.
Now if the relay does click and if the meter lamp does turn on
while keyed, is there any power output from the amp.
No output can mean blown power transistors (commonly called
pills).

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Re: Texas star DX500

Post by sonoma » Thursday, 15 February 2018, 4:27 AM

this portion he had posted covers checking the pills. this info I had saved from a retired amp builder. see if this info helps you. I wish I could remember his name. hate getting old .

Now we need to determine if the transistors are ok or if they are blown.
With the power turned on read the voltage on the top lead (collector) of the
transistors. We want full B+ here, 13.8 volts d.c.
More than that and you blew the transistors. Less than that and you have an open
circuit. This is connected directly to the fuse connector.
Now check the voltage at the bottom lead (base) of the transistors. This should read
00 volts d.c.
If you read any voltage here now, you have leaky transistors. They will need to be
replaced. Read the cautions in next section.
You can check the transistors without removing them, but you do need to get them
out of the circuit. This is called floating the transistors. Carefully lift the top tabs
(collectors) so they do not touch the traces. Now carefully remove the bottom tabs
(bases) so that they do not touch the traces. The transistor pair is now out of the
circuit. Now you need to check the resistances.
Connect the black lead of your ohmmeter to the top tab and the red lead to the
bottom lead. This is your collector base junction and it should read about 600 ohms.
Now connect the black lead to the ground trace (emmiter) and the red lead to the
bottom tab (base). This should also read about 600 ohms. It will be common to find
open or shorted junctions. This indicates a blown transistor. If these resistances are
as I say, the transistors are good.
Before changing transistors please read the cautions in the next section.
Burnt bias resistors always indicates blown transistors.
When changing the two 10 ohm resistors you will be well advised to also change the
1.6 or 1.8 ohm resistor also.


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Re: Texas star DX500

Post by sonoma » Thursday, 15 February 2018, 10:58 AM

295 I just emailed you the complete set of pages he had on his web site. he use to have a mail in business for amp repairs for a few years after he retired from texas star . at least that was what he had stated on his web site.

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Re: Texas star DX500

Post by 295 antenna » Friday, 16 February 2018, 18:27 PM

Ok so i was introduced to a gentleman who is supposed to be good at repairing amps .He hooked up the amp and its works perfectly. he thinks it got out of balance from the high dead key of the browning (11 watts) so now im on a quest to find out what was done to give the browning such a high dead key. gotto love radio
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