Defective PA HL2??? Please advise.

[Jan Damme_pa3abk]

Have HL2 for about 2 years now (aug 2021), but the PA is possible defective.
Or at least it is "not responding" correctly.
HL2 is running from a Raspberry Pi4.

There is no RF output, but idle current of the PA=+/-300mA  in QUISK (also in SparkSDR).
The current depends on the temperature, it is somewhat less by "cold" start.
With PTT "down" "Spot"-slider on zero.
In Rx zero mA.

The unit itself uses in idle (no tx, rx only) 189mA, with PTT down (no carrier) 437mA.
This to exclude that there is something wrong with the measuring device inside.
Enable PA = false (in QUISK) -> O mA and low power available on RF1.

There is no way to adjust the idle current and I don't see the communication between in the terminal of QUISK when I put them at 0.
(As showed in the YT video:
    -Connected to speedy
    -Response 125 received.)
Q: How can I see the communication between QUISK and the HL2 (under Linux)?

The unit has: Code version 73.2
QUISK version 4.2.18
LDMOS in this unit AFT503 XNUVPUA

(SparkSDR is reading the same data)

Understand from other posts that the PA is rather robust, so I was also thinking of a SW problem.
Glitch?
Consider to reload the RBF file (but never did that before) or forcing the factory file during start-up.

We had some thunderstorms yesterday, not heavy (distance).
But assume that will be not the cause.

The value 300mA puzzles me...

Any advise how to proceed is welcome.

Jan/pa3abk

[Steve Haynal]

Hi Jan,

If I understand correctly, you are seeing the expected 17-19dBm low power output when the PA is disabled?

With the PA enabled and during transmit, I'd check that VPA is the expected 8V. See here for where to measure VPA:

https://github.com/softerhardware/Hermes-Lite2/wiki/Hardware

To eliminate any software questions, I'd also test with CW key.

Check that the wiring for T3 (large transformer) still looks good and all wires are soldered.

73,

Steve

kf7o

[Jan Damme_pa3abk]

Thanks Steve for your quick response.

The "low power" is available and completely within the specs. I checked that with an scope/dummy.
I also had a look at the gate of both LDMOS devices.
During transmit the HF component on both is not symmetrical at all.
Possible one or both of the LDMOS devices didn't survive...
The drainvoltage of both is 8V.

There are two places which are not populated with resistors. (R128 & R129) which enabled me to measure the output P1B & P0B of U15 MCP4662. Both gave 0V.
I am not familiar with this IC but assume it is "resistor" which can be adjusted via the bus.

Gate measurements of the LDMOS devices.
DC component 51mV & 60mV (Spot slider in QUISK min)
AC component 80mV & 680mV (both @ 18MHz) (Spot slider in QUISK max)

The PA idle current (in QUISK program) is stable around 300mA, somewhat lower at cold start.
With or without HF there is (almost) no difference.

Based I have measured now, I suspect that both LDMOS are defective, probably a shortcut between Gate and Source.
Second I suspect U15. The latter is not likely because if there is a "shortcut" between gate & source, there is no DC, bearing in mind that I measure in "mV range" on the gate.

Third  The RF front end is working well in RX, but possible the changeover RX/TX some of the devices in that circuit is not performing.

The adjustment of the idle current in QUISK doesn't have any effect. If there is shortcut in de LDMOS devices this understandable, it pulls down the bias toward mV level.

How can I check that U15/MCP4662 is performing?

Jan/pa3abk

Op donderdag 22 juni 2023 om 06:06:06 UTC+2 schreef softerh...@gmail.com:

[Jan Damme_pa3abk]

Further I measured the resistance between Gate and Source of PA MOSFETs. Both are low ( Q3 14 Ohm and rev pol of meter same 14 Ohm, Q4 4 Ohm rev  pol same.)

Have the feeling they died because of the temperature at the mom here... We suffered with 35deg C shacktemp (no airco) assume inside the HL2 it was much higher.
HL2 unit was using WSPR on 18MHz. According the metering gave a 6W output when alive...

Intend to replace them, but original mosfet AFT05M, seems difficult to obtain.
The unit I have,  has originally 2x AFT 503 XNUVPUA inside.
They are available at AliExpress.

The original mentioned in the documentation AFT05MS003 seems difficult to obtain.
Intend to order a 5 pack AFT503 in CN.

Any suggestions/advise?

 
Jan/pa3abk

Op zaterdag 24 juni 2023 om 14:17:02 UTC+2 schreef Jan Damme_pa3abk:

[Steve Haynal]

Hi Jan,

Yes, the AFT05MS003 is difficult to find and is no longer in production. The latest HL2 builds use the AFT05MS004. I recommend you replace with AFT05MS004. This also requires changing R92 and R99 from 270 Ohm to 220 Ohm. See these posts as well as the thread the posts are in:

https://groups.google.com/g/hermes-lite/c/aKoqQCjjXNs/m/KBVrEe3VAAAJ

https://groups.google.com/g/hermes-lite/c/aKoqQCjjXNs/m/-6N8mco6BQAJ

73,

Steve

kf7o

[Jan Damme_pa3abk]

Thanks Steve,

I'm nearsighted... so without glasses I am able to see the finest details. 

Replacing the FET should not be a problem, but the resistors...

Removing the "old" by the "new" sometimes the PCB will be damaged.

I was thinking to just parallel them with 1k2 resistor on top of them, it will be a "one go solder job". Just "ticking" with some flux and solder.

The calculated result will be 220 Ohm.

However it will add some extra capacitance... Assume that this will not extreme effect the bandwidth of the PA.

 Understand that the resistors used are "0603" types.

Assume that you sourced the AFT05MS004 at Mouser?  
Mouser partno: 841-AFT05MS004NT1 

At the moment can't find them in NL parts shops, besides MOUSER.NL and CN Ali. 

With the latter I'm a bit hesitant, due its reputation of "counterfeit" products.

Jan/pa3abk

Op maandag 26 juni 2023 om 18:31:45 UTC+2 schreef softerh...@gmail.com:

[Steve Haynal]

Hi Jan,

I think 1KOhm resistors in parallel with the existing 270Ohm resistors should be okay. I don't think there will be enough extra capacitance to cause a problem.

Yes, you can source them at Mouser. There are other sources which may be better for you:

https://octopart.com/search?q=AFT05MS004&currency=USD&specs=0

https://www.findchips.com/search/AFT05MS004

NXP may also send you a couple of sample parts:

https://www.nxp.com/part/AFT05MS004N#/

Regarding the rework of your board, some people have had success taking the board to a local phone repair shop. If you can tell them exactly what must be done, they usually have the skills to do some small surface mount repairs.

73,

Steve

kf7o

[Jan Damme_pa3abk]

For NL readers  -> found Distrilec is selling the FET their partno 302-62-261 @ €2,86/ea (exVAT).
Included a desoldering pincet w/acc in order to complete their min order value €25. Delivery within 24 hours!
Only problem could be, "as a private person" you can only pay via Paypal or Creditcard (Visa/Master) not via iDeal.

Steve, your tip regarding phone repair shop crossed my mind, but saw an "easy to use" desolderingtool and included that in the order.
It also opens up possibilities to handle smd sized projects.
Thanks for your assistance.

Jan/pa3abk

Op dinsdag 27 juni 2023 om 18:58:13 UTC+2 schreef softerh...@gmail.com:

[Cesc Gudayol]

Hi Jan

Can you give me a link to this "desoldering tool" you mention? I just damaged my finals and I need to replace them.

Did you succeed in replacing the PA MOSFETs? Any advice?

Thanks.

Cesc / ea3igt

[DL1YCF]

To replace the finals in my 300-Watt-PA, I bought a „ZD 915“ desoldering station.
This worked very well, perhaps you search the internet for it.

> --
> You received this message because you are subscribed to the Google Groups "Hermes-Lite" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to hermes-lite...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/4a5786ef-9b3a-4164-a386-0e8d49c11f40n%40googlegroups.com.

[Jan Damme]

It's  DISTRILEC partno 303-07-968. Price  € 15,60  (CN origine)
https://www.distrelec.nl/en/desoldering-tweezers-48w-rnd-lab-rnd-560-00288/p/30307968?queryFromSuggest=true&itemList=suggested_search
Extra 7 tips : 303-07-968 € 10,71
https://www.distrelec.nl/en/desoldering-tweezer-tips-30mm-7pcs-rnd-lab-rnd-560-00289/p/30307969
Assume you either locate a local supplier or CN website will offer this
also.
Distrilec is able to ship it to your country.

This tool makes it possible to remove "small" parts, but also complete
IC's within seconds. It works like a pincet, all pins are heated at once
and with almost no effort you can retract the "defective" part.
The fault I made "blowing up" the PA was  PEBKAC -> Another TX was
errorneously switched to the PA of HL2. (No issue of design of HL2)

Do note that solder is "lead free" don't attemp to use "lead" solder,
but use "lead  free" solderpaste and heat airgun. Clean the area with
isopropanol before replacement.
Otherwise it wil contaminate giving bad result....
Jan/pa3abk



Op 18-11-2023 om 19:23 schreef Cesc Gudayol:

> Hi Jan
>
> Can you give me a link to this "desoldering tool" you mention? I just
> damaged my finals and I need to replace them.
>
> Did you succeed in replacing the PA MOSFETs? Any advice?
>
> Thanks.
>
> Cesc / ea3igt
>
> On Tuesday, June 27, 2023 at 7:47:56 PM UTC+2 Jan Damme_pa3abk wrote:
>
>
> For NL readers  -> found Distrilec is selling the FET their partno
> 302-62-261 @ €2,86/ea (exVAT).
> Included a desoldering pincet w/acc in order to complete their min
> order value €25. Delivery within 24 hours!
> Only problem could be, "as a private person" you can only pay via

> Paypal or Creditcard (Visa/Master) _not_ via iDeal.

> MOUSER.NL <http://MOUSER.NL> and CN Ali.

> --
> You received this message because you are subscribed to a topic in the
> Google Groups "Hermes-Lite" group.
> To unsubscribe from this topic, visit
> https://groups.google.com/d/topic/hermes-lite/NZhMOspX1GU/unsubscribe.
> To unsubscribe from this group and all its topics, send an email to

> hermes-lite...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/hermes-lite/4a5786ef-9b3a-4164-a386-0e8d49c11f40n%40googlegroups.com

> <https://groups.google.com/d/msgid/hermes-lite/4a5786ef-9b3a-4164-a386-0e8d49c11f40n%40googlegroups.com?utm_medium=email&utm_source=footer>.

[Steve Haynal]

Hi Cesc,

For removal of multipin SMT devices, I prefer hot air. There are several under $100 options:

https://www.amazon.com/WEP-8786D-I-SE-Desoldering-Hot-Air-Nozzles/dp/B0BXN5NXFQ/ref=sr_1_26?crid=2N9XKUF1QPOT3

Does your HL2 use the AFT05MS004N or AFT05MS003N in the PA? I can send you a pulled device if you like.

73,

Steve

kf7o

[Cesc Gudayol]

Thank you Steve but I carefully tested my Hermes Lite and the finals are in good condition, so there’s no need for a replacement.
Also, I’m grateful to Christoph and Jan for their valuable suggestions.

73

Cesc / ea3igt