Re: [Drakelist] TR-7 Transmit issues

[Bob Fish]

Thanks Joe, 
Mouser has them for a buck and a half. That's more like it.

Bob K6GGO

Sent from my iPad

On Dec 20, 2011, at 4:15 PM, Joe Pyles  wrote:

> again, 

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Re: [Drakelist] TR-7 Transmit issues

[Joe Pyles]

I use NTE229 to replace the MPSH20 on the predriver board and they work fine.

73, Joe KC9LAD

At 06:57 PM 12/20/2011, you wrote:
Sorry about that, I sent the e-mail before I was done typing. Does 
anyone have source for an MPS-H20. It looks like they aren't 
available. I found a reference to it on the Drake mods
document. The guy says he replaces them with MRF237 because it can 
handle a little extra power. Apparently, he thinks the TO-92 package 
was border line undersized for .3 watts.
Maybe that's why mine is going south (I've been running digital 
modes). I found these MRF237s on Ebay for 8 bucks (stick'em up). 
I'll pay it if I have to. Any thoughts?



Bob  K6GGO

Well, it seems that the first transistor on the driver board is the 
culprit. Or, at least, when the transmitter fails, that is where 
the RF stops. It is a Motorola MPS-H20

I found the schematic on Ron's site. Thanks Lee.

Bob  K6GGO

Hi Guys,
Thanks for the replies. The first thing I thought to do was 
re-seat the boards and I did. Well, I didn't re-seat the ones 
that were hidden under
the display board (DR-7).  I'll take it apart and re-seat them if 
I have to, but, I think I have isolated the problem to the 
pre-driver board and it
doesn't plug into anything. It is bolted to a heatsink next to 
the PA. When it is in a failed condition, I have RF going into, 
but not out of, the pre-driver board.


Thanks for the offer, but I already have a set of extender boards.

I will find the problem eventually , I just need a schematic. I 
will take another look at Ron's site.


Thanks again,

Bob  K6GGO






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Re: [Drakelist] TR-7 Transmit issues

[Robert Fish]

Sorry about that, I sent the e-mail before I was done typing. Does 
anyone have source for an MPS-H20. It looks like they aren't available. 
I found a reference to it on the Drake mods
document. The guy says he replaces them with MRF237 because it can 
handle a little extra power. Apparently, he thinks the TO-92 package was 
border line undersized for .3 watts.
Maybe that's why mine is going south (I've been running digital modes). 
I found these MRF237s on Ebay for 8 bucks (stick'em up). I'll pay it if 
I have to. Any thoughts?



Bob  K6GGO

Well, it seems that the first transistor on the driver board is the 
culprit. Or, at least, when the transmitter fails, that is where the 
RF stops. It is a Motorola MPS-H20

I found the schematic on Ron's site. Thanks Lee.

Bob  K6GGO

Hi Guys,
Thanks for the replies. The first thing I thought to do was re-seat 
the boards and I did. Well, I didn't re-seat the ones that were 
hidden under
the display board (DR-7).  I'll take it apart and re-seat them if I 
have to, but, I think I have isolated the problem to the pre-driver 
board and it
doesn't plug into anything. It is bolted to a heatsink next to the 
PA. When it is in a failed condition, I have RF going into, but not 
out of, the pre-driver board.


Thanks for the offer, but I already have a set of extender boards.

I will find the problem eventually , I just need a schematic. I will 
take another look at Ron's site.


Thanks again,

Bob  K6GGO







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Re: [Drakelist] TR-7 Transmit issues

[Robert Fish]

Well, it seems that the first transistor on the driver board is the 
culprit. Or, at least, when the transmitter fails, that is where the RF 
stops. It is a Motorola MPS-H20

I found the schematic on Ron's site. Thanks Lee.

Bob  K6GGO

Hi Guys,
Thanks for the replies. The first thing I thought to do was re-seat 
the boards and I did. Well, I didn't re-seat the ones that were 
hidden under
the display board (DR-7).  I'll take it apart and re-seat them if I 
have to, but, I think I have isolated the problem to the pre-driver 
board and it
doesn't plug into anything. It is bolted to a heatsink next to the 
PA. When it is in a failed condition, I have RF going into, but not 
out of, the pre-driver board.


Thanks for the offer, but I already have a set of extender boards.

I will find the problem eventually , I just need a schematic. I will 
take another look at Ron's site.


Thanks again,

Bob  K6GGO







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Re: [Drakelist] TR-7 Transmit issues

[Robert Fish]

I found the schematic on Ron's site. Thanks Lee.

Bob  K6GGO

Hi Guys,
Thanks for the replies. The first thing I thought to do was re-seat 
the boards and I did. Well, I didn't re-seat the ones that were hidden 
under
the display board (DR-7).  I'll take it apart and re-seat them if I 
have to, but, I think I have isolated the problem to the pre-driver 
board and it
doesn't plug into anything. It is bolted to a heatsink next to the PA. 
When it is in a failed condition, I have RF going into, but not out 
of, the pre-driver board.


Thanks for the offer, but I already have a set of extender boards.

I will find the problem eventually , I just need a schematic. I will 
take another look at Ron's site.


Thanks again,

Bob  K6GGO







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Re: [Drakelist] TR-7 Transmit issues

[Robert Fish]

Hi Guys,
Thanks for the replies. The first thing I thought to do was re-seat the 
boards and I did. Well, I didn't re-seat the ones that were hidden under
the display board (DR-7).  I'll take it apart and re-seat them if I have 
to, but, I think I have isolated the problem to the pre-driver board and it
doesn't plug into anything. It is bolted to a heatsink next to the PA. 
When it is in a failed condition, I have RF going into, but not out of, 
the pre-driver board.


Thanks for the offer, but I already have a set of extender boards.

I will find the problem eventually , I just need a schematic. I will 
take another look at Ron's site.


Thanks again,

Bob  K6GGO



Hi Bob:

Before jumping right to looking for a flaky component, have you done 
the requisite re-seating of the board?  Deoxit on the edge connector, 
and relay cleaning?


FWIW

Curt
KU8L


On 12/20/2011 3:15 PM, Robert Fish wrote:

Hi Guys,
I have a two part question. I noticed a few weeks ago that, on 
occasion, my TR-7 would not transmit when keyed. If I unkey and then 
key again, it would transmit.
I noticed when running digital modes, which I do using VOX for keying 
the transmitter. Well, the last few days it has become more frequent. 
It also happens in cw.
If I key the transmitter 10 times, maybe 3 or 4 times Ill get no RF 
out. I traced the problem to the pre-driver board. I always have RF 
in, but when it fails there is no RF going to the PA.
Even though I have an early TR-7, I have the later version of the 
driver board. Unfortunately, I only have the schematic for the early 
version in my service manual.


Where can I get a schematic for the later pre-driver board?

Any idea what is happening here? It shouldn't be too much trouble to 
figure out which component is going flakey, if I can get a print for 
the newer board.


Thanks in advance,

Bob  K6GGO

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Re: [Drakelist] TR-7 Transmit issues

[J. Steven Cochrane]

Before you start replacing parts clean the Band Switch contacts and reseat 
the boards. That usually fixes it for another year.

Steve

J. Steven Cochrane W7JSC


- Original Message - 
From: "Robert Fish" 
To: 
Sent: Tuesday, December 20, 2011 1:15 PM
Subject: [Drakelist] TR-7 Transmit issues


> Hi Guys,
> I have a two part question. I noticed a few weeks ago that, on occasion,
> my TR-7 would not transmit when keyed. If I unkey and then key again, it
> would transmit.
> I noticed when running digital modes, which I do using VOX for keying
> the transmitter. Well, the last few days it has become more frequent. It
> also happens in cw.
> If I key the transmitter 10 times, maybe 3 or 4 times Ill get no RF out.
> I traced the problem to the pre-driver board. I always have RF in, but
> when it fails there is no RF going to the PA.
> Even though I have an early TR-7, I have the later version of the driver
> board. Unfortunately, I only have the schematic for the early version in
> my service manual.
>
> Where can I get a schematic for the later pre-driver board?
>
> Any idea what is happening here? It shouldn't be too much trouble to
> figure out which component is going flakey, if I can get a print for the
> newer board.
>
> Thanks in advance,
>
> Bob  K6GGO
>
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Re: [Drakelist] TR-7 Transmit issues

[Curt]

Hi Bob:

Before jumping right to looking for a flaky component, have you done the 
requisite re-seating of the board?  Deoxit on the edge connector, and 
relay cleaning?


FWIW

Curt
KU8L


On 12/20/2011 3:15 PM, Robert Fish wrote:

Hi Guys,
I have a two part question. I noticed a few weeks ago that, on 
occasion, my TR-7 would not transmit when keyed. If I unkey and then 
key again, it would transmit.
I noticed when running digital modes, which I do using VOX for keying 
the transmitter. Well, the last few days it has become more frequent. 
It also happens in cw.
If I key the transmitter 10 times, maybe 3 or 4 times Ill get no RF 
out. I traced the problem to the pre-driver board. I always have RF 
in, but when it fails there is no RF going to the PA.
Even though I have an early TR-7, I have the later version of the 
driver board. Unfortunately, I only have the schematic for the early 
version in my service manual.


Where can I get a schematic for the later pre-driver board?

Any idea what is happening here? It shouldn't be too much trouble to 
figure out which component is going flakey, if I can get a print for 
the newer board.


Thanks in advance,

Bob  K6GGO

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[Drakelist] TR-7 Transmit issues

[Robert Fish]

Hi Guys,
I have a two part question. I noticed a few weeks ago that, on occasion, 
my TR-7 would not transmit when keyed. If I unkey and then key again, it 
would transmit.
I noticed when running digital modes, which I do using VOX for keying 
the transmitter. Well, the last few days it has become more frequent. It 
also happens in cw.
If I key the transmitter 10 times, maybe 3 or 4 times Ill get no RF out. 
I traced the problem to the pre-driver board. I always have RF in, but 
when it fails there is no RF going to the PA.
Even though I have an early TR-7, I have the later version of the driver 
board. Unfortunately, I only have the schematic for the early version in 
my service manual.


Where can I get a schematic for the later pre-driver board?

Any idea what is happening here? It shouldn't be too much trouble to 
figure out which component is going flakey, if I can get a print for the 
newer board.


Thanks in advance,

Bob  K6GGO

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