Deaf Lowe HF 225 Europa - UK Vintage Radio Repair and Restoration Discussion Forum

netsmo62 · 16th Jul 2023, 3:40 pm

Hello, I have already dealt with this Lowe on this forum here https://www.vintage-radio.net/forum/...d.php?t=201868 but due to a frequency memorization problem, which unfortunately cannot be easily resolved for now. In the meantime, a new problem emerged, the radio first began to crackle and then after some work to eliminate this problem it became deaf. To facilitate understanding, I have uploaded a video on YT at this address https://youtu.be/TgEug_4qXBI in which you can first see the radio receiving, let's say regularly but with the crackling already present, crackling that progressively increases ... I have identified the problem in the three corroded areas that are seen as a fixed image in the video, I cleaned up the whole area, also disassembling some parts or replacing it like the D27 with another BA244. After that, as seen in the video, the signal has collapsed almost to zero, what you can barely hear is a 5 Mhz signal modulated with 1 V amplitude, and so it remains with any type of filter inserted. I also tried to try to follow the modulated signal through a signal tracer, but the results were uncertain, it is not clear where the problem could be. I've already checked the components and double-checked the leads and welds but haven't found anything out of place. the AF section has been tested with the classic signal injector and works perfectly. I checked the voltages on the three RF-IF integrated circuits, Q1-Q2 and Q3 and on the first two I didn't find any relevant anomaly, while on Q3 (also supported by the same test done on my standard HF225) the most obvious anomaly is a voltage on pin 4 (2nd IF input amplifier) I find only 0.455V instead of the expected 0.8. Then other anomalies always lower than what is indicated on SM pin 3-3.08V (3.6) pin 8-3.6V (4.0) pin 15-0.75V (0.9) pin 16-2.3V (3.7). I also tested all the switching diodes including those of the input bandpass filters and they are all OK.

On page 26 of the SM there is a description of a procedure for testing the various stages of the receiver, only that we are talking about frequency selective level meters, but such an instrument costs hundreds and hundreds of euros... what could I use as an alternative? Thanks in advance, F.

John KC0G · 16th Jul 2023, 7:13 pm

Hello F,

The archives at the Lowehfreceivers group at groups.io, https://groups.io/g/LoweHFReceivers/ , of which you are a member, contain horror stories of battery leakage in HF-150's. If you had alkaline cells in that radio and then plugged in an external 12 Volt supply, the radio would try to charge the cells. I would run away from any HF-150 which had had battery leakage.

And so, what caused the corrosion in the HF-225 Europa? Was a battery pack installed in the radio and if so, did it leak? You may be looking at a real labour of love to attempt to repair this radio.

Sorry, but this is not encouraging. But it is the way that I see it.

73 John KC0G/M0KCY

Cruisin Marine · 16th Jul 2023, 7:27 pm

You won't need a selective level meter, just a signal generator ac coupled in with a 1nF or similar.
Page 25 of the manual gives the expected levels like: 1st mixer input, Q1 pins 12 and 13 expect 65uV at 14.201 MHz.
There are plenty more measurement points mentioned in the manual.

http://www.f6hoy.com/wp-content/uplo...25_service.pdf

Tracing a receiver fault without a signal generator is a road to nowhere though.
I hope you took the board out fully and cleaned both sides with some Isopropyl Alcohol?
Your friend is a very close visual inspection with a jewellers loupe or similar.

netsmo62 · 16th Jul 2023, 10:38 pm

Thanks for reply, I have both DDS Signal Generator FY6900 (if you have seen video) than a professional digital multimeter, a HP3466A. But since I think these are RF measurements surely I will need to connect a RF probe prior to test key points...

Hi, F.

Cruisin Marine · 16th Jul 2023, 10:52 pm

You don't need a probe, just inject the RF signal via an open ended lead with a 1nF coupling cap to the point mentioned above. Keep the leads to the capacitor fairly short if possible of course.
If it if deaf there go further down the receive chain to narrow it down. You won't need any fancy meters, just listen to the speaker output.

The results won't be exact, but you will soon find out where the receiver is failing badly.

netsmo62 · 18th Jul 2023, 10:47 pm

Ok, I have take the page 26 table with various frequency and points and try to injected modulated signals as you have suggested through a 1nf capacitor. In brief, from A to K I have nothing or almost nothing until I connected pin 6 & 7 of Q3 at 455.4 Khz, where s-meter go to full scale and hear clear modulated sound.

Put the same level and fq on pin 4 gets almost nothing, so when I connected signal just before C75 or anode of D26-27...SL6700 faulty?

Hi, F.

Cruisin Marine · 19th Jul 2023, 7:28 pm

I am reluctant to get too involved as it is a piece of eqpt I have never used or even seen.
I reiterate, to make sure that your repair is successful you will need to remove the board and clean both sides (and re solder/re-flow solder) before you carry on, as any corrosion will just carry on eating away at tracks and components.
It may seem daunting, but is a must, there is no shortcut.

If you don't, more faults will develop in future and you will never win.
You may well have corrosion between the pins on the SL 6700 chip and various other places, a thorough clean will save you much time and grief in the long run.

Sparky67 · 19th Jul 2023, 9:48 pm

I have used white vinegar in the past to remove PCB corrosion due to battery leakage, and it works very well. What you don’t see are damaged vias leading through from one side of the board to the other and tracks under ICs, so checking those for continuity on your radio might be a good thing to do, if you haven’t already.

netsmo62 · 22nd Jul 2023, 4:28 am

Corrosion on the board are already defeated. In the end problem is the SL6700C for sure, I have made the same test on pin 4 of SL6700C of my standard Lowe HF225 and there it works perfectly, I correctly hear the modulated note through loudspeaker.

I have just received the spare SL6700C now is a matter to use a desoldering station to desolder IC without harm the pads and tracks.

Hi, F.

16th Jul 2023, 3:40 pm	#1
netsmo62 Tetrode Join Date: Nov 2020 Location: Nonantola (MO), Italy Posts: 56	Deaf Lowe HF 225 Europa Hello, I have already dealt with this Lowe on this forum here https://www.vintage-radio.net/forum/...d.php?t=201868 but due to a frequency memorization problem, which unfortunately cannot be easily resolved for now. In the meantime, a new problem emerged, the radio first began to crackle and then after some work to eliminate this problem it became deaf. To facilitate understanding, I have uploaded a video on YT at this address https://youtu.be/TgEug_4qXBI in which you can first see the radio receiving, let's say regularly but with the crackling already present, crackling that progressively increases ... I have identified the problem in the three corroded areas that are seen as a fixed image in the video, I cleaned up the whole area, also disassembling some parts or replacing it like the D27 with another BA244. After that, as seen in the video, the signal has collapsed almost to zero, what you can barely hear is a 5 Mhz signal modulated with 1 V amplitude, and so it remains with any type of filter inserted. I also tried to try to follow the modulated signal through a signal tracer, but the results were uncertain, it is not clear where the problem could be. I've already checked the components and double-checked the leads and welds but haven't found anything out of place. the AF section has been tested with the classic signal injector and works perfectly. I checked the voltages on the three RF-IF integrated circuits, Q1-Q2 and Q3 and on the first two I didn't find any relevant anomaly, while on Q3 (also supported by the same test done on my standard HF225) the most obvious anomaly is a voltage on pin 4 (2nd IF input amplifier) I find only 0.455V instead of the expected 0.8. Then other anomalies always lower than what is indicated on SM pin 3-3.08V (3.6) pin 8-3.6V (4.0) pin 15-0.75V (0.9) pin 16-2.3V (3.7). I also tested all the switching diodes including those of the input bandpass filters and they are all OK. On page 26 of the SM there is a description of a procedure for testing the various stages of the receiver, only that we are talking about frequency selective level meters, but such an instrument costs hundreds and hundreds of euros... what could I use as an alternative? Thanks in advance, F.

16th Jul 2023, 7:13 pm	#2
John KC0G Hexode Join Date: Mar 2009 Location: Minneapolis, Minnesota, USA. Posts: 278	Re: Deaf Lowe HF 225 Europa Hello F, The archives at the Lowehfreceivers group at groups.io, https://groups.io/g/LoweHFReceivers/ , of which you are a member, contain horror stories of battery leakage in HF-150's. If you had alkaline cells in that radio and then plugged in an external 12 Volt supply, the radio would try to charge the cells. I would run away from any HF-150 which had had battery leakage. And so, what caused the corrosion in the HF-225 Europa? Was a battery pack installed in the radio and if so, did it leak? You may be looking at a real labour of love to attempt to repair this radio. Sorry, but this is not encouraging. But it is the way that I see it. 73 John KC0G/M0KCY

16th Jul 2023, 7:27 pm	#3
Cruisin Marine Heptode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 989	Re: Deaf Lowe HF 225 Europa You won't need a selective level meter, just a signal generator ac coupled in with a 1nF or similar. Page 25 of the manual gives the expected levels like: 1st mixer input, Q1 pins 12 and 13 expect 65uV at 14.201 MHz. There are plenty more measurement points mentioned in the manual. http://www.f6hoy.com/wp-content/uplo...25_service.pdf Tracing a receiver fault without a signal generator is a road to nowhere though. I hope you took the board out fully and cleaned both sides with some Isopropyl Alcohol? Your friend is a very close visual inspection with a jewellers loupe or similar. __________________ "Behind every crowd, there's a silver Moonshine"

16th Jul 2023, 10:38 pm	#4
netsmo62 Tetrode Join Date: Nov 2020 Location: Nonantola (MO), Italy Posts: 56	Re: Deaf Lowe HF 225 Europa Thanks for reply, I have both DDS Signal Generator FY6900 (if you have seen video) than a professional digital multimeter, a HP3466A. But since I think these are RF measurements surely I will need to connect a RF probe prior to test key points... Hi, F.

16th Jul 2023, 10:52 pm	#5
Cruisin Marine Heptode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 989	Re: Deaf Lowe HF 225 Europa You don't need a probe, just inject the RF signal via an open ended lead with a 1nF coupling cap to the point mentioned above. Keep the leads to the capacitor fairly short if possible of course. If it if deaf there go further down the receive chain to narrow it down. You won't need any fancy meters, just listen to the speaker output. The results won't be exact, but you will soon find out where the receiver is failing badly. __________________ "Behind every crowd, there's a silver Moonshine" Last edited by Cruisin Marine; 16th Jul 2023 at 11:22 pm.

18th Jul 2023, 10:47 pm	#6
netsmo62 Tetrode Join Date: Nov 2020 Location: Nonantola (MO), Italy Posts: 56	Re: Deaf Lowe HF 225 Europa Ok, I have take the page 26 table with various frequency and points and try to injected modulated signals as you have suggested through a 1nf capacitor. In brief, from A to K I have nothing or almost nothing until I connected pin 6 & 7 of Q3 at 455.4 Khz, where s-meter go to full scale and hear clear modulated sound. Put the same level and fq on pin 4 gets almost nothing, so when I connected signal just before C75 or anode of D26-27...SL6700 faulty? Hi, F.

19th Jul 2023, 7:28 pm	#7
Cruisin Marine Heptode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 989	Re: Deaf Lowe HF 225 Europa I am reluctant to get too involved as it is a piece of eqpt I have never used or even seen. I reiterate, to make sure that your repair is successful you will need to remove the board and clean both sides (and re solder/re-flow solder) before you carry on, as any corrosion will just carry on eating away at tracks and components. It may seem daunting, but is a must, there is no shortcut. If you don't, more faults will develop in future and you will never win. You may well have corrosion between the pins on the SL 6700 chip and various other places, a thorough clean will save you much time and grief in the long run. __________________ "Behind every crowd, there's a silver Moonshine" Last edited by Cruisin Marine; 19th Jul 2023 at 7:33 pm.

19th Jul 2023, 9:48 pm	#8
Sparky67 Heptode Join Date: Feb 2008 Location: Great Barr, Sandwell, West Midlands, UK. Posts: 589	Re: Deaf Lowe HF 225 Europa I have used white vinegar in the past to remove PCB corrosion due to battery leakage, and it works very well. What you don’t see are damaged vias leading through from one side of the board to the other and tracks under ICs, so checking those for continuity on your radio might be a good thing to do, if you haven’t already.

22nd Jul 2023, 4:28 am	#9
netsmo62 Tetrode Join Date: Nov 2020 Location: Nonantola (MO), Italy Posts: 56	Re: Deaf Lowe HF 225 Europa Corrosion on the board are already defeated. In the end problem is the SL6700C for sure, I have made the same test on pin 4 of SL6700C of my standard Lowe HF225 and there it works perfectly, I correctly hear the modulated note through loudspeaker. I have just received the spare SL6700C now is a matter to use a desoldering station to desolder IC without harm the pads and tracks. Hi, F.