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XV-144 Receiver RF Amp Bias Adjustments

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KJ4YQK

XV-144 Receiver RF Amp Bias Adjustments

R13 is not adjusting anything. 0 volts. I was wondering what to look for. Has anybody experience this, and what is the corrected action.
What voltage should I read at C4 D3 junction. Should it be 6.8 volts?

Thanks Dave

Don Wilhelm-4

Re: XV-144 Receiver RF Amp Bias Adjustments

Dave,

Yes, you should read 6.8 volts to ground at the C4 D3 junction.

Make certain you have voltage at both ends of R15. If you do, then
check the soldering carefully in the upper left quadrant of the board.

73,
Don W3FPR

On 7/23/2011 1:00 AM, KJ4YQK wrote:
> R13 is not adjusting anything. 0 volts. I was wondering what to look for.
> Has anybody experience this, and what is the corrected action.
> What voltage should I read at C4 D3 junction. Should it be 6.8 volts?
>
> Thanks Dave
>
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KJ4YQK

RE: XV-144 Receiver RF Amp Bias Adjustments

Hi Don,

Tnxs for the reply. I broke a resister R14, lifting one end to read. It check good before the lead broke off. Head to Radio Shack to pick up a new one. I did not get the 6.8 volt at the C4 D3 Junction. I will retouch the solder joints with the iron to see if it comes back. Will pick up an extra D3 while I am radio shack just in case.

David

From: Don Wilhelm-4 [via Elecraft] [mailto:[hidden email]]
Sent: Saturday, July 23, 2011 8:21 AM
To: KJ4YQK
Subject: Re: XV-144 Receiver RF Amp Bias Adjustments

If you reply to this email, your message will be added to the discussion below:

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Don Wilhelm-4

Re: XV-144 Receiver RF Amp Bias Adjustments

David,

If you found zero volts at D3, then R12 is not fully soldered. OTOH, if
you found close to 12 volts, D3 is not doing its job.

Good luck on finding parts at RS if it is anything like the store in my
area.

73,
Don W3FPR

On 7/23/2011 9:38 AM, KJ4YQK wrote:

> Hi Don,
>
>
>
> Tnxs for the reply. I broke a resister R14, lifting one end to read. It
> check good before the lead broke off. Head to Radio Shack to pick up a new
> one. I did not get the 6.8 volt at the C4 D3 Junction. I will retouch the
> solder joints with the iron to see if it comes back. Will pick up an extra
> D3 while I am radio shack just in case.
>
>

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KJ4YQK

RE: XV-144 Receiver RF Amp Bias Adjustments

Hi Don,

I had to order some resistors on line, got a box of them now. I am still not getting the voltage that I should be getting. I check for 12R voltage at the top of R16 and C29 and see nothing. 12R voltage comes from the K5 relay.

I check the run between K5 to R16 it looks good.

I check the output of U4 and it is good. Looking at the schematics I think I should be getting 12 volts from U4 via K5 12R.. The schematics are showing K5 in it’s natural state with no power apply. I am not seeing any connection between K5 and U4 (I am thinking pin1) or none of the pins on the board. I see where U4 should have 0 ohms to one of the pins in K5 but don’t see it.

Having problem finding the board run between U4 and K5.

Am I reading this right?

Thanks David

From: Don Wilhelm-4 [via Elecraft] [mailto:[hidden email]]
Sent: Saturday, July 23, 2011 1:18 PM
To: KJ4YQK
Subject: Re: XV-144 Receiver RF Amp Bias Adjustments

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KJ4YQK

Re: XV-144 Receiver RF Amp Bias Adjustments

In reply to this post by Don Wilhelm-4

Hi Don,

Reposting Here I don't think my post are making in via outlook. Anyway here is where I am at.

1. Yes I have 12 volts on the cathode of D14, but no voltage on the anode. D19 had 12 volts on the cathode and 6 volts on the anode.

2. Been over the jumpers about 10 times now. My settings are as follow on page 9.
JP1: 1-2 JP2:2-3 JP9: 1-2
1 milliwatt JP3: 1-2 JP4:1-2 JP5 2-3 JP6 2-3

JP7 Shorting block has jumper on it and no shorting block on JP8

Front Panel Board has a jumper on JP1.

3. Not sure if you got my last email. Just in case. I was thinking Q3 might be bad because I had to move it from the front side of the board to the back side. I pulled Q3 and it check good. I went ahead and replace it with a new one.

4. Retouch most of the solder joints around the relays and the pre-amp section. Including the R12.

Question (not sure if I have this right in my reading of the diagrams): Q3 (front panel) sends a ground to D14 (main board) when the radio is power up by a positive signal from U4(front panel). The PWR En signal maybe, just wondering if I am reading this right. If a ground appears on the anode of D14 the diode causing forward bias, and the voltage should drop below 12 volts to like 6 volts causing K4 to activate.

Thanks David

Don Wilhelm-4

Re: XV-144 Receiver RF Amp Bias Adjustments

David,

First - those diodes across the relays do not control anything, they are
there only to absorb the reverse polarity voltage kickback when the
relay opens. That means when a relay is active, you will have 12 volts
on the cathode and close to zero on the anode. So K4 is activated, but
K5 is questionable.

6 volts on the anode of the diode is not good. That would say there is
some current going through K5, perhaps enough to lift the armature off
the NC contact, but not enough to close the NO contact.

The control of relay K5 is Q2 on the front panel board. I suspect that
transistor may have a collector to base short or leakage. If there is
near volts on the base, the collector should be open circuit (K5 not
activated), but when the base voltage rises to 0.6 volts or more, Q2
should conduct fully and pull relay K5 in (transmit condition).

There is an error on the IF and Control Schematic. The input to U4
connects to the 12PRI voltage source instead of 12V as indicated on the
schematic. There is no way that power can get to the firmware chip if
it as shown. I just traced the PC connections on an image of the board
and U4 connects to the cathode end of D14 (12PRI)

With your JP8 jumper in place, closing the front panel switch pulls in
relay K3 which puts 12 volts on the regulator and in turn sends 5 volts
to the firmware chip and wakes it up - the firmware chip raises the
voltage on pin 12 which causes Q3 to conduct, pulling K4 in. K5 should
still be open (both the cathode and anode of D15 should be at 12 volts)
and should remain so until transmit is asserted by closing the KEY IN
signal.

73,
Don W3FPR

On 7/30/2011 4:22 PM, KJ4YQK wrote:

> Hi Don,
>
> Reposting Here I don't think my post are making in via outlook. Anyway here
> is where I am at.
>
> 1. Yes I have 12 volts on the cathode of D14, but no voltage on the anode.
> D19 had 12 volts on the cathode and 6 volts on the anode.
>
> 2. Been over the jumpers about 10 times now. My settings are as follow on
> page 9.
> JP1: 1-2 JP2:2-3 JP9: 1-2
> 1 milliwatt JP3: 1-2 JP4:1-2 JP5 2-3 JP6 2-3
>
> JP7 Shorting block has jumper on it and no shorting block on JP8
>
> Front Panel Board has a jumper on JP1.
>
>
> 3. Not sure if you got my last email. Just in case. I was thinking Q3
> might be bad because I had to move it from the front side of the board to
> the back side. I pulled Q3 and it check good. I went ahead and replace it
> with a new one.
>
> 4. Retouch most of the solder joints around the relays and the pre-amp
> section. Including the R12.
>
>
> Question (not sure if I have this right in my reading of the diagrams): Q3
> (front panel) sends a ground to D14 (main board) when the radio is power up
> by a positive signal from U4(front panel). The PWR En signal maybe, just
> wondering if I am reading this right. If a ground appears on the anode of
> D14 the diode causing forward bias, and the voltage should drop below 12
> volts to like 6 volts causing K4 to activate.
>
> Thanks David
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/XV-144-Receiver-RF-Amp-Bias-Adjustments-tp6612768p6636816.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
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KJ4YQK

Re: XV-144 Receiver RF Amp Bias Adjustments

I replaced Q2 and now I have the voltage on R16, and I am able to change the Receiver RF Ap bia. Starting it off at 179 mV. I am able to get it above 200 with no problems. One transister off, at least I have two good transisters nwo.

Updating the Schematic now for the IF and Control circuits.

I plan on getting this up on the air tonight, maybe in time for the local 2 meter net.

Thanks for helping me out, this really gave me a good look at the circuits. I will write some notes on it.

I will look at the correction you mentions abt the circuit board. What effect does that have on the operation of the unit if left as is?
David

Don Wilhelm-4

Re: XV-144 Receiver RF Amp Bias Adjustments

David,

Well, most all XV transverters out there have this problem and operate
without obvious symptoms. The situation is that there is no diode
across the K5 coil to absorb the "kickback" voltage from the relay coil
inductance when the power to it is removed. If you find the time
between transmit and receive slowed, then that change will help the
situation. Actually, there is a path present through the contacts of
K4, so the diode is still doing its job as long as K4 remains closed
(and it normally will). It is just better to have the diode connected
directly across the K5 relay coil.

All I am saying is that if you get a chance to remove the bottom cover
for any reason, that is a good time to make the modification - if there
is no reason to remove the bottom panel, then leave it as-is for now.

73,
Don W3FPR

On 7/30/2011 7:31 PM, KJ4YQK wrote:

> I replaced Q2 and now I have the voltage on R16, and I am able to change the
> Receiver RF Ap bia. Starting it off at 179 mV. I am able to get it above
> 200 with no problems. One transister off, at least I have two good
> transisters nwo.
>
> Updating the Schematic now for the IF and Control circuits.
>
> I plan on getting this up on the air tonight, maybe in time for the local 2
> meter net.
>
> Thanks for helping me out, this really gave me a good look at the circuits.
> I will write some notes on it.
>
> I will look at the correction you mentions abt the circuit board. What
> effect does that have on the operation of the unit if left as is?
>
> David
>

Colin VE3MSC

Re: XV-144 Receiver RF Amp Bias Adjustments

Don - do you mean diode across the K6 and K7 relay coil or do you
mean connect at the NO contact of K5 ? From schematic in Rev E Owner
Manual, it looks like K5 normally open contact provides 12T that
connects to both K6 and K7 coils. The PN2222 preamp + MAR3 are
powered by same 12T, and I expect a negative spike would be bad there.

At 08:48 PM 2011-07-30, Don Wilhelm wrote:

>David,
>
>Well, most all XV transverters out there have this problem and operate
>without obvious symptoms. The situation is that there is no diode
>across the K5 coil to absorb the "kickback" voltage from the relay coil
>inductance when the power to it is removed. If you find the time
>between transmit and receive slowed, then that change will help the
>situation. Actually, there is a path present through the contacts of
>K4, so the diode is still doing its job as long as K4 remains closed
>(and it normally will). It is just better to have the diode connected
>directly across the K5 relay coil.
>
>All I am saying is that if you get a chance to remove the bottom cover
>for any reason, that is a good time to make the modification - if there
>is no reason to remove the bottom panel, then leave it as-is for now.
>
>73,
>Don W3FPR
>
>On 7/30/2011 7:31 PM, KJ4YQK wrote:
> > I replaced Q2 and now I have the voltage on R16, and I am able to
> change the
> > Receiver RF Ap bia. Starting it off at 179 mV. I am able to get it above
> > 200 with no problems. One transister off, at least I have two good
> > transisters nwo.
> >
> > Updating the Schematic now for the IF and Control circuits.
> >
> > I plan on getting this up on the air tonight, maybe in time for
> the local 2
> > meter net.
> >
> > Thanks for helping me out, this really gave me a good look at the circuits.
> > I will write some notes on it.
> >
> > I will look at the correction you mentions abt the circuit board. What
> > effect does that have on the operation of the unit if left as is?
> >
> > David
> >
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html

Don Wilhelm-4

Re: XV-144 Receiver RF Amp Bias Adjustments

Colin,

No, I mean that D15 would be better connected directly to the coil of K5.
Right now, the cathode of D15 is connected to the cathode of D14.
You can cut that short trace between the diode cathodes and solder a
short jumper from the cathode of D15 to the K5 coil + side - it will be
connected to the right place if you wire to the relay pin (K5 common)
just to the right (looking at the bottom side) of the cathode end of D15.

In actual practice, it it not critical that the change be made.

73,
Don W3FPR

On 8/4/2011 7:01 AM, Colin VE3MSC wrote:
> Don - do you mean diode across the K6 and K7 relay coil or do you
> mean connect at the NO contact of K5 ? From schematic in Rev E Owner
> Manual, it looks like K5 normally open contact provides 12T that
> connects to both K6 and K7 coils. The PN2222 preamp + MAR3 are
> powered by same 12T, and I expect a negative spike would be bad there.
>
>
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Colin VE3MSC

Re: XV-144 Receiver RF Amp Bias Adjustments

Ok, I understand what you mean. I'll open up the XV and compare to
the schematic, as it shows the D15 across the coil, cathode not to
D14. But nothing across K7, K6 coils on schematic.
I've had a problem with output spikes on switching sometimes - power
meter will show 1 bar for a fraction of a second. Sometimes the XV
will blink all the powerbar lights and need a reset. Been trying to
track this down. I slowed my rig QSK to 20ms from 15ms, and that
helped a lot. Still seeing something not right.

At 08:09 AM 2011-08-04, Don Wilhelm wrote:

>Colin,
>
>No, I mean that D15 would be better connected directly to the coil of K5.
>Right now, the cathode of D15 is connected to the cathode of D14.
>You can cut that short trace between the diode cathodes and solder a
>short jumper from the cathode of D15 to the K5 coil + side - it
>will be connected to the right place if you wire to the relay pin
>(K5 common) just to the right (looking at the bottom side) of the
>cathode end of D15.
>
>In actual practice, it it not critical that the change be made.
>
>73,
>Don W3FPR
>
>On 8/4/2011 7:01 AM, Colin VE3MSC wrote:
>>Don - do you mean diode across the K6 and K7 relay coil or do you
>>mean connect at the NO contact of K5 ? From schematic in Rev E Owner
>>Manual, it looks like K5 normally open contact provides 12T that
>>connects to both K6 and K7 coils. The PN2222 preamp + MAR3 are
>>powered by same 12T, and I expect a negative spike would be bad there.
>>

Don Wilhelm-4

Re: XV-144 Receiver RF Amp Bias Adjustments

Colin,

The XV blinking all the powerbar lights is quite a different problem
which really has a simple solution (in all cases I have seen it). In
some setups, it seems that noise is coupling onto the signal line to the
firmware IC which triggers that situation (pin 26). A .001 to .01 uF
capacitor between the collector and emitter of Front Panel Q2 has cured
it in all cases I have seen. You might try adding that capacitor.

Capacitors across a relay coil can also "swallow" the back EMF kick when
the relay opens. Note that capacitors C85 and C61 are electrically
across the coils of both relays (and K1 too).

73,
Don W3FPR

On 8/4/2011 8:36 AM, Colin VE3MSC wrote:

> Ok, I understand what you mean. I'll open up the XV and compare to
> the schematic, as it shows the D15 across the coil, cathode not to
> D14. But nothing across K7, K6 coils on schematic.
> I've had a problem with output spikes on switching sometimes - power
> meter will show 1 bar for a fraction of a second. Sometimes the XV
> will blink all the powerbar lights and need a reset. Been trying to
> track this down. I slowed my rig QSK to 20ms from 15ms, and that
> helped a lot. Still seeing something not right.
>
> At 08:09 AM 2011-08-04, Don Wilhelm wrote:
>> Colin,
>>
>> No, I mean that D15 would be better connected directly to the coil of K5.
>> Right now, the cathode of D15 is connected to the cathode of D14.
>> You can cut that short trace between the diode cathodes and solder a
>> short jumper from the cathode of D15 to the K5 coil + side - it
>> will be connected to the right place if you wire to the relay pin
>> (K5 common) just to the right (looking at the bottom side) of the
>> cathode end of D15.
>>
>> In actual practice, it it not critical that the change be made.
>>
>> 73,
>> Don W3FPR
>>
>> On 8/4/2011 7:01 AM, Colin VE3MSC wrote:
>>> Don - do you mean diode across the K6 and K7 relay coil or do you
>>> mean connect at the NO contact of K5 ? From schematic in Rev E Owner
>>> Manual, it looks like K5 normally open contact provides 12T that
>>> connects to both K6 and K7 coils. The PN2222 preamp + MAR3 are
>>> powered by same 12T, and I expect a negative spike would be bad there.
>>>
>
> ______________________________________________________________
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