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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 10th Jan 2021, 3:54 pm   #1
richmond
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Default Lowe HF-150 power issue

It has been many years since I set eyes on my HF-150, but I have just dug it out of a storage box. The power adaptor was missing, but I found a 12v 2.5a mains adaptor and it powered up fine, although with interference.

It works well with batteries (8xAA), and no interference that I get with the AC power adaptor, and luckily the unit was stored without batteries installed so the battery compartments are very clean.

I would like to use the radio as a mobile unit, being able to power from a 12v vehicle battery (AA battery consumption is high/expensive). However, when I do this, I get the loPr (low battery power) on the screen and can't use the radio. There is no problem with the battery feed (it came from a new powerful battery on my Land Rover).

Any ideas on what the problem could be?

Also, any suggestions/links to a power supply without interference would be useful (but not as important as being able to get it to work from the car!)

Many thanks.
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Old 10th Jan 2021, 7:07 pm   #2
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Default Re: Lowe HF-150 power issue

The manual says 10 to 15V (nominal) so it should be OK, what voltage is measured inside the set when powered by the Landys battery?
 
Old 11th Jan 2021, 12:56 am   #3
majoconz
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Default Re: Lowe HF-150 power issue

The AC mains power supply is IMHO one of those blanket-blank switch mode things that radiate noise and whistles for miles around - well, quite some distance anyway.....
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Old 11th Jan 2021, 1:45 am   #4
SiriusHardware
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Default Re: Lowe HF-150 power issue

Not true, the original Lowe branded mains PSU (I have one) is a standard simple unregulated DC mains PSU (Transformer, bridge rectifier, capacitor). It's in the same 'ski jump' casing as the original Sinclair Spectrum power supply. Richmond mentioned that he 'found' a power supply which strongly implies it is not the original one.

Richmond may not remember, but when the radio is running from external DC it will try to charge the batteries as they are assumed to be Nicads or MiMHs. When powering the radio from external DC, remove the batteries if they are NOT rechargeable.

Last edited by SiriusHardware; 11th Jan 2021 at 1:51 am.
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Old 11th Jan 2021, 9:00 am   #5
richmond
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Default Re: Lowe HF-150 power issue

Correct, it is not the original power supply. I do not remember having any issues with the one I used previously, but I think that is lost for good. I am also not even sure if that was the original one or a replacement as I bought the item second hand many years ago.

I needed to flick through the manual to remind myself how to use the buttons, and did notice the piece about mains power charging batteries. I also remember how leaking batteries can cause a lot of damage to these units. I don't think I ever used them before. It stayed in the house mains powered, although I now wish to try taking on the road, powering from the vehicle or camping trailer (which has solar powered batteries). A pity to won't do that.

I will check the voltage inside the box later today.

Many thanks
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Old 11th Jan 2021, 12:16 pm   #6
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Default Re: Lowe HF-150 power issue

I still have the HF-150 that my original Lowe power supply belongs to, so out of interest I will try running it on a variable bench supply this evening to see at what input volts the 'LoPr' message comes up on mine.
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Old 11th Jan 2021, 2:52 pm   #7
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Default Re: Lowe HF-150 power issue

One further point to note is that (I believe) the radio only charges the batteries when the external DC power is applied and the power / volume control is set to 'off'. I think it 'rewires' the batteries as two parallel strings when charging, in order to derive a sufficiently high charging voltage per cell from the relatively low external DC input voltage.
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Old 11th Jan 2021, 7:56 pm   #8
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Default Re: Lowe HF-150 power issue

I've just done a quick test with my HF-150 being supplied with variable voltage through the EXT DC socket. If I start off at 12V and wind slowly down, the 'LoPr' indication comes on when the input voltage reaches 8.55V.

The unit takes 8 * AA size rechargeables so when running on a set of reasonably charged batteries their nominal total voltage will be 1.2V * 8 = 9.6V, so I would say that the 'LoPr' indication threshold is really aimed at telling you when the batteries are running low, not when the DC input voltage is low.

The next time you try your experiment can you remove one battery from each tray of four so you can be sure that the radio is actually running from power supplied from the DC input, and not just on run-down batteries? The problem is that the displays on these don't have any dedicated symbols to tell you if the radio is running on batteries / charging / running on EXT-DC so you have to prove those things by other means.

I observe that the DC plug on my real Lowe PSU is a 'long reach' type with approx 10mm of exposed outer metal barrel between the moulded 'cover' on the plug and the insulated plastic 'ring' around the end of the tip. The ring itself adds about 1.5mm of length to the overall length of the barrel so from the cover to the end of the tip it is almost 12mm.

The plug on the lead I used to carry out my test above has a shorter reach / shorter barrel and it would only just work / make contact at certain angles of rotation. So here is one hypothesis, your radio is not actually running on your external DC power supply because the plug on that 'found' PSU does not reach far enough into the socket.
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Old 11th Jan 2021, 8:21 pm   #9
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Default Re: Lowe HF-150 power issue

If you're actually doing the tests in the car, yes - make sure the plug is providing a proper earth and you're not getting a 'phantom' earth via the coax of the aerial.

In past-times it was quite common for bodge-installed car stereos to lose the negative connection but carry on working [to an extent] by earthing through the aerial-coax and the aerial-to-body contact.
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Old 11th Jan 2021, 9:06 pm   #10
richmond
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Default Re: Lowe HF-150 power issue

SiriusHardware - your hypothesis is correct. Spot on! There was a very slight difference in the length of the plugs. I did test the lead in another device (a rally trip meter) and it worked, so assumed it would work on the radio. I cut a different (slightly longer) plug off a redundant power block and wired it (with an inline fuse) directly to the battery, and the radio powered up and worked without low power messages.
I have now added a cigar lighter plug to the other end and am ready to go mobile

Many many thanks!! This site is great.
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Old 11th Jan 2021, 9:24 pm   #11
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Default Re: Lowe HF-150 power issue

If you ever have that problem in future you can, sometimes, convert a moulded 'short reach' power plug into a 'long reach' one by cutting off 2mm of the moulded cover to expose a bit more of the barrel at the 'cover' end - which in turn will then allow the plug to go a little bit deeper into the socket.

Whether you can do that depends on the shape and type of the moulded plug in question.
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