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 Post subject: HRO5TA1 vs. HRO5A1
PostPosted: Oct Sat 31, 2020 4:13 pm 
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Joined: Nov Wed 17, 2010 11:14 pm
Posts: 207
Good day,

In advance of obtaining a HRO5TA1 for restoration, I was looking at the manual on the 5A1.

Is there and electrical differences between these two National radios?

As far as I can tell from the little searching I have done, the T is for Table model. However, they both appear to be table models based on the pictures I have seen. And the front panel controls appear to be identical.

Thanks in advance, Alan


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Oct Sat 31, 2020 4:31 pm 
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Alan,

Electrically they are the same but National made a lot of variants within the HRO-5 and I suspect there were ongoing production changes as the state of the art rapidly evolved so don't be surprised to see variance between your model and published schematics. The big A suffix change is the noise limiter control. This was a wartime to civilian transition model so the original coils may or may not have band spread capability IF you get them with your radio.

The true rack model will have a front panel designed for rack mounting, unlike some other makers National did make different mechanical versions of their early receivers for rack or table mount while many competitors used a typical rack mount panel in a cabinet. As I recall, there are some subtle mechanical differences at least with some models and I remember a thread on one of the mailing lists where converting a rack mount to table mount required some additional shims or washers in the coil mount/locking and eject section for proper operation when it was transplanted to a new panel and case.

Rodger WQ9E


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Oct Sat 31, 2020 5:23 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Morris Plains, N.J. 07950
Here's everything you wanted to know about the HRO but were afraid to ask.

https://www.radioblvd.com/National%20HRO.htm


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Oct Sat 31, 2020 6:36 pm 
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Joined: Nov Wed 17, 2010 11:14 pm
Posts: 207
Thank you Rodger and Joe!

I did check the excellent info at the HRO site, Joe. Great info and history.

I believe the 4, A-C coils are all present as well the external supply.

I am reading the 5A1 manual, the only one I currently could find readily, although the unit may have the original manual as well. In any case, are there any documented technical goofs in the manual... or I may be misunderstanding the tech writer!

The radio is single conversion, 456 kHz IF with high side injection. Great! That places the image above the 2xRF input frequency, or 912 kHz. Yet the alignment if required for the HF LO reads per attached... and I am questioning, the image location is ABOVE the RF freq, the manual seems to state below??? Maybe I am reading this wrong.


Attachments:
File comment: from the manual
HF_LO_adj.jpg
HF_LO_adj.jpg [ 114.9 KiB | Viewed 963 times ]
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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Oct Sat 31, 2020 7:37 pm 
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Alan,

The wording is a bit awkward but what they mean, for example, is with a test signal at 10 Mhz. then the HFO should be at 10.456 Mhz. If you tune the RECEIVER 912 Khz. lower without changing the test signal frequency, then you should hear the 10 Mhz. test signal again as the image response with the HFO operating at 9.544 Mhz.

If instead you incorrectly adjusted the HFO to 9.544 Mhz to receive a 10 Mhz signal, then you are receiving the image while the correct setting would be at 10.456 when you tune it 912 Khz. higher.

To avoid any chance of this, I use an external shortwave receiver to listen for and set the HFO properly which is very fast and avoids the chance of tracking on the wrong side. A Grundig YB-400 has its place among the Tektronix and HP gear on my bench :)

Rodger WQ9E


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Oct Sat 31, 2020 8:13 pm 
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HRO5TA1 is the table model, HRO5RA1 is the rack mount there are a lot of subtle changes during the year or so when they were made 1946-1947. I have one of each, made 6 months apart and there are some differences between them but not enough to make restoring them any tougher


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Oct Sat 31, 2020 9:18 pm 
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Joined: Nov Wed 17, 2010 11:14 pm
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Got it Rodger. Thanks!

Next time I'll stand on my head and try again.

Yes, I agree or a frequency counter for sure.
Before I do any diddle diddle on any circuit, I'll first see what I have in hand.

Thanks for the clarification on the rack vs table version part number!

73' Alan


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Oct Sat 31, 2020 10:25 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Seattle WA US
FWIW, here's a link to the Army manual for the HRO series, which includes the HRO-5:

http://www.mediafire.com/file/65m1baofh ... l.pdf/file

While National manuals were far superior to Hallicrafters manuals of the same period, the military versions sometimes contain info that didn't reach the commercial manuals. Also here is a link to the UK EMER
military manual, which contains rare coil data:

http://www.mediafire.com/file/gfozp34dr ... A.pdf/file

Also some National bench test data for the HRO-5

http://www.mediafire.com/file/453m1e7rk ... 5.pdf/file

73
Chuck K7MCG


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Tue 03, 2020 5:38 pm 
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Joined: Nov Wed 17, 2010 11:14 pm
Posts: 207
Thanks Chuck for the added information and links.

The history on this receiver is quite rich!

I was not aware how the HRO name evolved. Quite a HOOT!

Here is another excellent link.

https://www.cryptomuseum.com/df/hro/index.htm

It has excellent references to a number of pdf's of the 5 and the other HRO units in the series.

Since my homebrew station is built around a several of James Millen's dial-drives, the HRO5 will take a proud spot on the table.... as soon as I make some room!

73' Alan


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Fri 06, 2020 8:17 pm 
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Joined: Nov Wed 17, 2010 11:14 pm
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Good day.

Here are some pix to share. The receiver is in amazing condition. Yep, will require TLC but all in all not bad. The basic coils are all there, A-D including the original storage box. The date code is July 1945. This radio may have decoded the battle front lines! All the pots are free to move, they feel silky and the xtal selectivity switch turns freely with positive position clicks. The dog house PS will require some work. Looks like the xmfr is an add on so I have to see what is going on in the dog house PS first. Probably do a basic wipe down and clean up and start with the power supply.

I have no speaker. I did find a 5k to 3.9 ohm xmfr in the junk box so I think I am good there. Unless there is an audio xmfr under the chassis of the radio, that xmfr will need to do.

The side antenna port terminals are not there. Added neatly is an SO239 UHF connector. I may seek out trying to put it back as original.

There are no odors, no nicotine colors and the only odor is the classic odor of electronics from the 1940's era!

Alan


Attachments:
HRO5_Rx_Front.jpg
HRO5_Rx_Front.jpg [ 233.74 KiB | Viewed 723 times ]
HRO5_Rx_coil_set.jpg
HRO5_Rx_coil_set.jpg [ 245.9 KiB | Viewed 723 times ]
HRO5_PS_view_pwr_port.jpg
HRO5_PS_view_pwr_port.jpg [ 207.47 KiB | Viewed 723 times ]
HRO5_PS_view_xmfr.jpg
HRO5_PS_view_xmfr.jpg [ 149.66 KiB | Viewed 723 times ]


Last edited by avictor on Nov Fri 06, 2020 10:59 pm, edited 1 time in total.
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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Fri 06, 2020 8:29 pm 
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Joined: Nov Wed 17, 2010 11:14 pm
Posts: 207
Here is a top down chassis view.

The chassis plate appears to be in very good condition.

Any advice in advance of digging in is most appreciated,

Thanks, Alan


Attachments:
HRO5_Rx_top_chassis.jpg
HRO5_Rx_top_chassis.jpg [ 199.8 KiB | Viewed 718 times ]
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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Sat 07, 2020 12:30 am 
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There was the code HRO-5; it came in two varieties, HRO-5R and HRO-5T
R= rack T=table
Then there was the code HRO-5A; it came in two varieties, HRO-5RA and HRO-5TA
Only difference was 5A had bandspread
Then there was the HRO-5A1; it came in two varieties, HRO-5RA-1 and HRO-5TA-1
Added two additional tubes. noise limiter

The "-" are important because without them it difficult to tell one from another.

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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Sat 07, 2020 12:55 am 
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it appears you have the late version of the 5TA1 as the added noise limiter tubes are mounted on the chassis instead of a raised sub chassis and the two limiter controls on the right hand side are spaced apart.


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Sat 07, 2020 3:01 am 
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Joined: Nov Wed 17, 2010 11:14 pm
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Thanks for the added information.

I have the 697 power supply apart. It appears the prior owner made some mods that are undocumented. The xmfr in the prior pix is a 12.6 V CT unit. I have no clue why it is in there. There is an additional filter cap and the original rect tube. The 80 rectifier tube is a Motorola to boot pre bat wings! It tests good. I will try to get a pix of what is there. My plan, is to pull what I do not understand and check the power xmfr and 17H choke, 6 v fil and 5 v fil as well HV. If they all check out, replace the original 3 section cap and re wire the 697 per the National sch.

My only guess, is he may have been using the 12.6 as a CT only to get 6.3 v fil and the fil xmfr which is potted went bad? There are also some bleeders R's in there as well. No clue.

Alan


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Sat 07, 2020 4:55 am 
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Joined: Nov Wed 17, 2010 11:14 pm
Posts: 207
Here are 3 pix on the PS type 697. I measured DCR for the 5 v, 6 v HV and choke. I will check the original HV cap. I assume it is the original as it has an appropriate retainer ring for mounting. The other filter cap in view, smaller one, no clue. The xmfr on the bottom is the 12.6 V and it appears he installed a dpdt sw to toggle between 6 and 12V AC out to the A+ terminal. Again, no clue. There are bleeders across HV, about 8 or so k, again no clue.

For the DCR values I get:

5 V and 6 V fil ~ 0 ohm... they look A-ok,

The 17 H choke at 280 ohm, seems reasonable,

The HV winding start to finish at 708 ohms and to the center tap, 343 and 365 ohms.

The 115 V primary a few ohms.

The HV winding R seems a bit high, but the rated total current is 75 mA. So should not be an issue.... Next to flame on the 115 V and see if all is well.

One other strange item is a bushing on the front panel of the HRO 5, to the right of the dial. Not sure if this was added by the owner or part of a mod by National?

Thanks for any info.


Attachments:
HRO5_PS1.jpg
HRO5_PS1.jpg [ 211.86 KiB | Viewed 675 times ]
HRO5_PS2.jpg
HRO5_PS2.jpg [ 192.28 KiB | Viewed 675 times ]
HRO5_PS3.jpg
HRO5_PS3.jpg [ 191.61 KiB | Viewed 675 times ]
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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Sat 07, 2020 6:26 am 
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Posts: 3567
Location: Fenton, MI 48430
Take out the two capacitor cans before power up and replace with a dual ARS capacitor glued in place here:
https://www.ebay.com/itm/16uf-16uf-500v ... XQlgtS81a9

Schematic below.

http://bama.edebris.com/download/nation ... %20697.pdf

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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Sat 07, 2020 3:35 pm 
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Joined: Nov Wed 17, 2010 11:14 pm
Posts: 207
Excellent Jim,

Thanks for the heads up to the added manuals on the BAMA site and the caps.

Just to be sure I have functional power xmfr, plan to remove the caps and the other mystery parts. Then test for V out AC and go from there. The main plan, re build the supply per the National sch. for the 697 power supply.

Any suggestions on the best method of cleaning the coil racks? The all appear in good mechanical shape. After the dirt and grime is removed from the graph legends, it appears they will be clear and crisp to read.


The same needs to be done with the receiver, S meter and care taken in any cleaning. I don't want to use stupid chemicals that do more damage then good.

Again, thanks!

Alan


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Tue 24, 2020 3:35 am 
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Joined: Nov Wed 17, 2010 11:14 pm
Posts: 207
I have spent a few part time days cleaning up the HRO5. The serial number is in clear view, #184-0346. Thanks to Henry Rogers at the Radio Blvd Western Radio Museum for helpful information.

The power supply is 100% functional and the new dual 16 uF 500 V C strapped into place. I added a line fuse and a 3 wire cord.

I have applied DEOXIT to the power plug and jack. They were heavily oxidized. Also DEOXIT to the coil rack contacts and the finger stock switch points in the HRO compartments.

The underside chassis after cleaning up some crazy wiring is pretty nice. This latter series HRO does not use bathtub caps on the rear wall. So there is ample room to mount an audio transformer. This was done by the prior user. Not sure of the speaker Z required, will check that out next.

There is a modification added which I am trying to search out. It is tacked into the last IF stage into the AVC, dual diode, and 2nd detector stage. Schematic attached. Series Blocking cap added at the point shown in the sch and routed out the cabinet rear via coax. I have some ideas but curious if anyone is familiar with this mod for the HRO5.


Attachments:
HRO5_cleaned.jpg
HRO5_cleaned.jpg [ 211.85 KiB | Viewed 499 times ]
HRO5_bottom_rewire1.jpg
HRO5_bottom_rewire1.jpg [ 290 KiB | Viewed 499 times ]
User_Mod_Sch.jpg
User_Mod_Sch.jpg [ 105.86 KiB | Viewed 499 times ]
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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Tue 24, 2020 4:09 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3659
Location: Seattle WA US
You said:
The side antenna port terminals are not there. Added neatly is an SO239 UHF connector. I may seek out trying to put it back as original.

The german silver antenna terminals ARE there, directly behind the aluminum plate that supports the added SO-239 antenna connector.
You can see them if you blow up the bottom left corner of photo <HRO5_Rx_top_chassis.jpg> shown above.

-Chuck


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 Post subject: Re: HRO5TA1 vs. HRO5A1
PostPosted: Nov Tue 24, 2020 6:22 am 
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Joined: Nov Wed 17, 2010 11:14 pm
Posts: 207
Correct Chuck. By the first inspection I missed the connector posts and the window to pass the open wire line is covered with a plate. The plate holds the SO239 connector and riveted to the case side. Anyway, yes its all there. I may put it back as it was originally.

Alan


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