1st Aug 2018, 7:31 am | #21 |
Heptode
Join Date: May 2014
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Re: HRO and BC348
Ref the added transformer...I wondered that. I was about to look when i tuned to All India radio on about 1MHz and got distracted....SWLing.
D |
1st Aug 2018, 9:54 am | #22 |
Dekatron
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Re: HRO and BC348
Don't forget that the TR switch on the AR88 and the B+ switch on the HRO have two different circuit regimes....
The TR switch on the AR88 does not isolate the HT from the sound output valves anode, the valves anode, output transformer primary and the tone correction capacitor that's connected between anode and chassis are connected to HT at all times. The B+ switch on the HRO isolates all load circuits. Lawrence. |
1st Aug 2018, 10:43 am | #23 | |
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Re: HRO and BC348
Quote:
My RF stages appear to have survived lots of coil pack changes but I've no idea about the state of my 6V6. Peter |
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1st Aug 2018, 11:41 am | #24 |
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Re: HRO and BC348
Out of interest, apart from the output valve, does the receiver that's the subject of this thread use metal IO valves or glass UX6?
Do any of the coil packs have bandspread? Lawrence. |
1st Aug 2018, 1:11 pm | #25 |
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Re: HRO and BC348
My HRO has glass valves.
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1st Aug 2018, 5:02 pm | #26 |
Hexode
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Re: HRO and BC348
Colin,
This is my HRO with the transformer mounted under the chassis. It is mounted over the HT link cut out which I carefully preserved in case any one wanted it back original. What is not shown is under the transformer I permanently mounted 2 series 6.8 Ohms WW ( 13.6 Ohms) resistors across the speaker terminals so that the transformer could never be completely open circuit. I cant remember but I think the transformer was 8 Ohms and the 13.6 was an arbitrary selection to give load but not excessive. Pete Last edited by G4_Pete; 1st Aug 2018 at 5:06 pm. Reason: WW added |
1st Aug 2018, 7:24 pm | #27 |
Heptode
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Re: HRO and BC348
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1st Aug 2018, 7:57 pm | #28 |
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Re: HRO and BC348
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1st Aug 2018, 9:27 pm | #29 |
Heptode
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Re: HRO and BC348
Thank you, Lawrence. That's a useful type.
Cheers Roger |
2nd Aug 2018, 12:26 pm | #30 |
Octode
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Re: HRO and BC348
I remember the regular Sunday morning GB2RS news broadcasts on 80m in the early 1970s. Due to ground wave the broadcasts used to work their way up country from various stations on the same frequency 3.65MHz. They might even have been on AM. My local one was from Derby and I think was from G2CVV, though I could often hear G2MI. After the broadcast was over, the operator would take calls under his own callsign.
G2MI, Bromley, Kent was the address of the RSGB QSL Bureau for many years. I have an HRO but it's not been in use for years. I don't have a full set of coil packs and think those I do have have been adjusted at some point to tweak coverage. It's in the round tuit queue. Always fancied a BC 348. There was one brought into school for a while and gave us lots of break-time fun. I always liked the 'cheese segment' tuning dial. I'm sure there was one at NVCF but fortunately I was spent out by then... |
2nd Aug 2018, 3:44 pm | #31 |
Hexode
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Re: HRO and BC348
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2nd Aug 2018, 7:26 pm | #32 |
Dekatron
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Re: HRO and BC348
If not familiar with the tuning dial/drive system and want to remove any of the bits for servicing/lubrication or whatever etc then check these two sites out first, in a nutshell the centre bearing hole in the tuning shaft bush is off-centre from the bushes outer bearing surface, the bush is also marked "top":
https://www.prismnet.com/~nielw/PW_N...l/hro_dial.htm https://aa7ee.wordpress.com/2015/02/...pw-gear-drive/ Lawrence. |
3rd Aug 2018, 2:24 pm | #33 |
Heptode
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Re: HRO and BC348
Sorry, I have been very busy. I shall examine the valves for IO as requested and feedback...
David |
3rd Aug 2018, 2:47 pm | #34 |
Dekatron
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Re: HRO and BC348
Output valve aside, metal valves were used in the later versions, glass valves in the earlier versions, the plug-in Xtal was also dispensed with on the later of the glass valved versions and all of the metal valved versions.
Lawrence. |
3rd Aug 2018, 3:26 pm | #35 |
Heptode
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Re: HRO and BC348
Mine seems to be all valves.
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3rd Aug 2018, 3:39 pm | #36 |
Dekatron
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Re: HRO and BC348
Yes, they would be valves....
Looks like the late version of the all glass valve receiver, usually known as the HRO MX, the S meter scale was usually white on them. Lawrence. Last edited by ms660; 3rd Aug 2018 at 3:47 pm. Reason: correction |
3rd Aug 2018, 3:51 pm | #37 |
Heptode
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Re: HRO and BC348
Mine is a browny amber S meter, which I have read means it started life as yellow amber and has aged. I still havent located a stamped s/n on mine. I have found a number, C390, stemcilled onto the chassis which may be a s/n 'repeat' but I am not sure. I need to remove the chassis from the case to see whether it is stamped out of sight by the aerial bind posts...but why it would be out of sight I can't understand.
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3rd Aug 2018, 4:04 pm | #38 |
Dekatron
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Re: HRO and BC348
I had one that had a white scale, calibrated in mA, apparently at some point there was a shortage of certain types of meters during the war.
Lawrence. |
3rd Aug 2018, 5:39 pm | #39 |
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Re: HRO and BC348
Mine is white and nought to one milliamp.
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3rd Aug 2018, 5:41 pm | #40 |
Nonode
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Re: HRO and BC348
Davids HRO is a curious one.
Either it has the internal crystal or else it is one without a crystal filter. We haven't seen a front panel picture so can't tell if the controls are there. Also interesting is the braid running from ground lug on crystal filter box / main tuning capacitor ground link. It is bolted to the top cap of the first IF valve. None of mine have that... I wonder if it was to stop some kind of pickup at IF? Thats the sort of tricks I have to get up to with the BC348 and 909kHz from Brookmans Park! |