Hi Garey..Problem solved. I removed the transformer...bottom core was
flush with circuit board. I carefully took it apart,reglued it so two
ends of "E" facing each other were touching. I accidently broke one
little leg off,reglued it at same time,put it all back together & it
works FB. All bands work like they should,and I have 23.8 volts at pin
2. Glad I checked 10 volts before I messed with everything,because it
was off,I must've bumped the little pot one of the countless times I
took the circiut board in & out.
Saved a TR7 from the parts pile!!!
Thanks a bunch!!
Best 73 Paul
-----Original Message-----
From: Garey Barrell [mailto:[email protected]]
Sent: Tuesday, April 14, 2009 10:11 AM
To: Drakedude
Subject: Re: [Drakelist] TR7 tuning issues
Paul -
Are you sure the core is glued? Possibly just beeswax that has softened
and let the core "drop" a little. Touch a soldering iron to the "gap"
and see what happens. There is almost certainly nothing wrong with the
transformer itself, just that the flux can't jump that gap! I suspect
if you correct the core you'll see the correct 24 VDC and be back in
business on all bands.
73, Garey - K4OAH
Glen Allen, VA
Drakedude wrote:
Gary..
Not sure if it ever worked on 20 from a cold start. I use this TR7 ( I
have three) primarily on 160....if I ever did venture to 20,which was
rarely,I never noticed because rig was warmed up already.
And yes,depressing the RCT button makes the display freewheel & climb
to 17 & 32 mhz. Problem must be in that little transformer on the
power supply board. I'll have to watch Epay for one to come available
Tnx fer all the help
Best 73 Paul AD3G
-----Original Message-----
From: Garey Barrell [mailto:[email protected]]
Sent: Monday, April 13, 2009 5:36 PM
To: Drakedude
Subject: Re: [Drakelist] TR7 tuning issues
Paul -
OK. There should be NO gap between the two halves of the core.
Originally they were super-glued together with of course no gap. The
voltage should be 23.5 - 24.5VDC. 20M is the "high" end of the "low"
VCO, and so the low voltage is quite likely the problem. The wire
loop
is wrapped around the transformer parallel to the board, and should be
at about the gap between the two core halves.
Has the radio ever worked on 20M for you?
If you press in the RCT button on the front panel, the VCOs should
free
run, and settle around 17 MHz up through 20M BANDSWITCH position, and
32
MHz on the 15 and 10M Bands.
73, Garey - K4OAH
Glen Allen, VA
Drakedude wrote:
Hi Gary
No external 10volt supply or extender boards. I changed out caps
C2108
,09,&10. Some improvement. Put in a new 24v reg. Still the same. The
little transformer is intact (E's facing each other),but there is a
gap between the two cores( "E's ),about 1/8". Is that normal? The top
"E" (facing towards board) is glued fast & has a wire wrapped around
it..I think just to hold it together from the looks of it,not sure.
Now,all bands come right up when the rig is fired up,except 20
meters,which starts around 9 or 10 Mhz & starts climbing. It finally
starts to work when voltage at pin 2 reaches 19 volts. Voltage at pin
2 never gets above 20.8 volts. Not sure where to go next. Bad
transformer on regulator board perhaps? Even though it looks good,no
way to really test it without extender cards. Cheaper to buy a board
from one of the GASP! board sellers on Ebay than buy a set of
extender cards
73 Paul
-----Original Message-----
From: Garey Barrell [mailto:[email protected]]
Sent: Monday, April 13, 2009 11:56 AM
To: Drakedude
Subject: Re: [Drakelist] TR7 tuning issues
Paul -
I'd do a little more investigation before just replacing the
regulator..... This is a DC-DC converter, and there are other
possible
trouble sources that are more likely than the regulator.
Do you have an extender card set? Service manual? ESR Meter? Do
you have +13V power supply??
If you have a 10V supply, it is easy to run this board outside of the
transceiver. When you have it out of the radio, carefully examine
T2101
to make sure the top core half is firmly in place. If it is, apply
+13V
to Pin 9, return to Pin 3. Then check voltages, etc. I would be
more suspicious of C2108, 09 and 10. During all of this, be
particularly careful not to bump R2103. If you have a DMM, measure
the voltage on Pin 10, ref to Pin 12 as accurately as possible. This
voltage determines the alignment of the entire radio and if it is
changed, a complete realignment will be necessary. So if R2103 is
disturbed, you
can try resetting it as closely as possible to the measurement you
just made.
73, Garey - K4OAH
Glen Allen, VA
Drakedude wrote:
Hi Gary
I checked transformer.....A OK. Pin 2 gives me from cold start abt
14 volts....over next 15 minutes,as rig warms up it climbs to about
19 volts and all bands start to work well. Switching to 20 meters
will make the voltage drop to about 14 volts,and then it climbs back
up to
abt 19 volts (20 meters only band that does this). Going to order a
new regulator in AM. Package of regulator looks different...I get a
NTE 1908 as a cross reference for the MC78L24C regulator. No heat
sink...not sure it will work (100ma). Perhaps NTE 972 looks
better.....rated at 1 amp & heat-sinkable,and still 24v pos
regulator
Thanks
Paul AD3G
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Garey Barrell
Sent: Sunday, April 12, 2009 5:55 PM
To: [email protected]
Subject: Re: [Drakelist] TR7 tuning issues
Paul -
I'm assuming that the receiver is also NOT tuning correctly using
the analog dial..??
IF so, your Low Band VCO is "sorta" working, and the High Band VCO
is
completely unlocked.
First step is to look with a flashlight at the Power Supply board,
just behind the GAIN and DELAY pots at the front right corner. Be
VERY careful to NOT bump any of the row of pots along the top of
that board.
Anyway, near the bottom on the left side of that card is a small
transformer that has two "E" shaped cores, "facing" each other,
i.e.,
the three ends of the "Es" touching each other. One is trapped
under
the coil and wiring, but the other is just glued on top of the
other.
If you see three "fingers" pointing towards the front panel, the top
core has fallen off, and will be found when you carefully remove the
bottom cover of the TR-7. It can just be super-glued back on. If
you
see a smooth rectangular top with part numbers, then that is NOT
your problem!
Next would be to measure the +24VDC supply on Pin 2 of that card.
If
it's not there, check the transformer again or perhaps you have a
bad
regulator chip U2103. If the +24VDC is there, then further trouble
shooting will be necessary.
73, Garey - K4OAH
Glen Allen, VA
Drakedude wrote:
*/My TR7 started a new problem today.......some bands won't tune
properly.....80 mtrs won't go up past 3.500 (using up/down buttons)
and 20 meters and 10 meters the display just "runs wild" it keeps
climbing in frequency. PTO tuning has no effect on 20 & 10. No AUX
board installed./*
*/It's as though synthesizer is only partly working,due to some
bands
work OK (160,40,15) some half work (80) and two don't work at all
(20 & 10)/*
*/I reseated all the cards which had no effect. Any thoughts as
where to start looking?/*
*//*
*/Thanks, Paul AD3G/*
No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 8.5.285 / Virus Database: 270.11.56/2058 - Release Date: 04/14/09
06:17:00
_______________________________________________
Drakelist mailing list
[email protected]
http://mailman.zerobeat.net/mailman/listinfo/drakelist
