Power output issue, Excessive PA message with HLSetup program

[Jose Berrios]

After various attempts to correct the bias settings, I ran the latest hl2setup program and I am consistently getting this message from the setup program:

Start of tests...
Test the background noise level
Test the feedback signal level
Test the filters
Set the bias on the power output transistors...
Set bias on the power output transistors FAILED
PA current is 0.0; should be 10.00 10.0% - FAIL

I am concluding that I may have damaged the HL2 or N2ADR board beyond my ability to repair. Any useful feedback is appreciated.

[Steve Haynal]

Hi wb2bwu,

Why did you need to correct the bias settings? The bias is properly set by Makerfabs before shipping.

For the hl2setup program, a loop back with 30dB attenuator is required. Did you use that?

Please work through relevant steps on this wiki page:

https://github.com/softerhardware/Hermes-Lite2/wiki/No-Transmit

In particular, please report the voltages you measure and if RF signal is produced when attempting CW transmit from the front panel connector.

73,

Steve

kf7o

[Jose Berrios]

IPlease examine the attached document. It shows the testing I've performed thus far. There is still more testing to be done; however, the issue appears to be in the PA section.

[Jose Berrios]

Here is a shot of the two Mosfets in the PA area.

[Jose Berrios]

Viewing link to my Google doc: 

https://docs.google.com/document/d/1nBu5ZRDmM-zJKjC_jaUtLDhCFc0H0LPhiqiClfiCgvo/edit#heading=h.4lcbxztjgm71

[Steve Haynal]

Hi wb2wu,

Please provide a photograph of the bottom side of the circuit board near the mounting hole, similar to the photo you provided of the top.

Did TX at full power work and then stop working?

Please share your order date and Makerfabs order number for warranty purposes.

73,

Steve

kf7o

[Richard Neese]

what application are you using windows or linux based ?

pihpsdr you have to set the power limit in the pa section in the menu and then slide the power slider to full but you have to figure the correct power for each band

[wb2bwu]

Here are the answers to your questions:

Did TX at full power work and then stop working?

 Yes, Hermes operated at full power for a while before stopping working. I occasionally noticed temperatures over 40 C. It does produce a low-power signal.

Please share your order date and Makerfabs order number for warranty purposes.

I purchased the unit in July 2023 but only assembled it in January. It had been operating until the recent issue with the power output. 

I realize the unit is out of warranty; however, I am willing to pay for repairs. I am awaiting delivery of a second unit, but I want this one fixed.

Here are some shots I just took.

Joe (aka Jose) Berrios, B.S., M.S., RETIRED

 WB2BWU

Lifetime Memberships:

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WB2BWU 

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MY Cell Phone: 646-634-2789

Google Voice: (917)-930-4036 - please leave a message.

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[Steve Haynal]

Hi Joe,

We need to see the bottom side of the PCB (board must be removed) near the screw hole by the PA to determine if some components have been stripped off. 

With over 2000 boards sold, there is no financial incentive equal to or less than the cost of a HL2 board which would motivate me to take repairs. I only do an occasionally domestic warranty repair.I try to provide discussion and information on this list which can help others potentially repair a HL2 which we can continue with. Your HL2 may be repairable but it is still difficult to tell if it is a simple repair. Maybe someone else will agree to take a look if payment is involved. Maybe someone is interested in buying a broken HL2 on www.qrz.com, www.ebay.com or the Facebook group. There is no buying or selling allowed on this group due to bad past experiences. 

73,

Steve
kf7o

[wb2bwu]

Understood. I'll take a picture of the bottom and send it to the group.

Joe (aka Jose) Berrios, B.S., M.S., RETIRED

 WB2BWU

Lifetime Memberships:

• American Radio Relay League - ARRL
• The Radio Amateur Satellite Corporation (AMSAT)
• City College of New York Alumni Organization
• Quarter Century Wireless Association

WB2BWU 

Admin: CCNY Alumni Hams Group (TGIF 32780)

MY Cell Phone: 646-634-2789

Google Voice: (917)-930-4036 - please leave a message.

Email:  wb2...@gmail.com

Skype: live:wb2bwu

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/ca97aab0-d823-4214-9112-48dfee1ed91an%40googlegroups.com.

[wb2bwu]

Here is a picture of the bottom, as requested:

Joe (aka Jose) Berrios, B.S., M.S., RETIRED

 WB2BWU

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/ca97aab0-d823-4214-9112-48dfee1ed91an%40googlegroups.com.

[wb2bwu]

With the shim in place:

Joe (aka Jose) Berrios, B.S., M.S., RETIRED

 WB2BWU

[Ron Lewkowicz]

It looks like both J32 and C84 were sheered off while installing the heat shim. 

[wb2bwu]

THIS IS POWER COMING OUT!  Notice the PA current? 

Joe (aka Jose) Berrios, B.S., M.S., RETIRED

 WB2BWU

Lifetime Memberships:

• American Radio Relay League - ARRL
• The Radio Amateur Satellite Corporation (AMSAT)
• City College of New York Alumni Organization
• Quarter Century Wireless Association

WB2BWU 

Admin: CCNY Alumni Hams Group (TGIF 32780)

MY Cell Phone: 646-634-2789

Google Voice: (917)-930-4036 - please leave a message.

Email:  wb2...@gmail.com

Skype: live:wb2bwu

On Sat, Mar 23, 2024 at 10:02 PM wb2bwu <wb2...@gmail.com> wrote:

I don't see that. How come the power output is at .2 watts, while it was 5 watts and over for a while with the shim installed?

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/e82b5237-b1ed-46e9-a020-fb1da94117adn%40googlegroups.com.

[wb2bwu]

It putting out enough of a signal to be heard:

[Steve Haynal]

Hi Jose,

From your picture, it appears that components J32 and C84 are missing. See the picture below with the red arrows. Can you please confirm if they are truly missing. The HL2 will generate low power output of 0.2W if these components are missing.

Also, I think some thermal paste is conductive. You may want to check that and clean any excessive thermal paste.

73,

Steve

kf7o

[wb2bwu]

Thanks - I will confirm. I ordered replacement parts.

The shim installation is the weak point of this project. Before I proceed, I will have to learn how to handle SMD component installation safely.

Joe (aka Jose) Berrios, B.S., M.S., RETIRED

 WB2BWU

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[G4ZAL]

Hi Jose,

Many of us with 'early' HL2 don't have a heat shim and it works just fine (although I don't do long digi-mode type transmissions).

Installation of the heat shim requires a little care, but is easy enough if you follow the guide (I installed one in my 2nd HL2).

https://github.com/softerhardware/Hermes-Lite2/wiki/Final-Assembly#heat-shim

Good luck with your repair.

Nigel

G4ZAL

[Max]

Agree with Nigel. Never installed heat shim on my first HL2. Admittedly it's in the larger case, but have operated long period on WSPR and FT4/FT8 and all other modes and never had an issue. PA temp does sometimes rise into the low 40s C on hot summer days (UK) but never enough to auto-shutdown. 40C is not excessive for most components. CPUs on PCs can hit 100C and still survive!

On the board, as Ron said, looks like those two parts have been sheared off by incorrect/heavy handed heat shim installation. If in doubt, leave it off. Resoldering SMD not too challenging with a decent magnifier (you can wear two pairs of cheap reading glasses over the top of each other for many jobs). Small soldering iron tip. Ideally  a flux pen and some desoldering braid for clean--up. Loads of very helpful videos on YouTube about soldering/desoldering SMD parts. 

73

Max

[wb2bwu]

I still do not understand what caused the unit to lose power after operating ok at higher power.  The shim must have been in place properly for the unit to operate. It is possible for overheating caused the components to fall off. I didn't see any sign of that when I opened the unit. Can someone provide a plausible scenario that causes the unit to operate normally and then suddenly go to a lower power.

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/8c3a8d12-c360-4c7a-961b-7592764038c6n%40googlegroups.com.

[Steve Haynal]

Hi Jose,

Did you confirm that the components are indeed missing?

Here is a hypothesis. The connections of those two components to the PCB were weakened during the heat shim installation and/or weak to begin with as that area contains a lot of ground plane so can be hard to solder components. They were initially electrically connected so that the unit produced 5W. At some point during heated operation or mechanical movement/impact or tightening of the screw, these components finally detached. They were never noticed loose in the enclosure as they are very small.

From what I can see on qrz.com, you live in New York City. I think you should be able to find a phone repair shop, another ham or even a hungry engineering student willing to solder replacements on for a small fee. I would start by first installing these two missing components. You may have to reset your bias after that since you did adjust it previously. Hopefully neither of the LDMOS devices nor the Vpa regulator were damaged during operation with those two missing components.

73,

Steve

kf7o

[wb2bwu]

I'm contacting another ham who owns a Hermes Lite and has the technical skills to complete the repair after receiving the replacement components. I ordered extra LDMOS devices in case the existing ones were damaged.

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/85a247d6-806a-4fd7-a0e5-28eeb6422dc6n%40googlegroups.com.

[wb2bwu]

I received my new Hermes Lite 2 today. The picture below is from the new board.

I see the parts on the new unit; when I look at the previous unit, I see that J32 and C84 are missing.