HRO-60 QUESTIONS

[n2len]

Hello Everyone,
On my bench is a HRO-60 that needs quite a bit of work.
The last time the rig was used the previous owner said to me that after it being on for sometime he remembers a terrible smell. The main HV transformer was burning and melted wax/tar was oozing from the top of the transformer casing. He immediately shut it down. It was still working. Never looked at it again.
I can see the dried up wax/tar residue, it leaked into the cabinet as well. Before I bring this up on a variac, I read on the Internet to remove or change a .01 paper bypass cap from the transformer to ground. Do you know of this capacitor? Part number or location? C118 is listed on the internet, but that's a barrel type and .1 at 600 vlts and listed as a plate filter cap. Could they be c63 and c64 ac line caps? Then I read the dual ganged 40uf in the metal can?
I want to at least confirm by bringing up the receiver to see if the transformer is still alive. Any suggestions would be greatly appreciated.

I am planning on ordering replacements for All the Elemenco paper caps and black beauties.

Has anyone refinished the HRO-60 cabinet with paint? If so, recommended paint match? Ive been thinking about having the cabinet power coated but looking at the etched lettering, not too deep and maybe the coating will fill the etchings? I'm not looking to do a ground up restore, just electrical upgrades and make it look presentable in the shack.

Pics to follow....
Thanks....
 

[n2len]

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[n2len]

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[n2len]

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[ke7trp]

Thats an early HRO60.  The later radios has Cermic disks.  I would just order the Orange drop "KIT" from Tubes and more dot com.  They work great for Bypass and the value in the kit is nice. 

My advice here is simple.  Work tube by tube.  Check/replace every cap and resistor. I cant help with C118 as that is clearly not an AC cap.  All Papers should be replaced. The BB will probably be ok, But I would replace. 

Please,  Do something about the Xtal Phasing coupling now.  They always seem to come loose and then you have to take the rig apart again to fix it. 

As for paint, Just take the bottom cover in and match it.  HRO paint was many different colors.  I have a 50, 60 and a 183D including speakers and NONE of it matches exactly Len.

These radios where known for transformer failures..  The best way to figure this out is to replace the caps and then check the current draw.  The Trans might shot.

C

[WD5JKO]

I sometimes zoom in when the pictures are high quality; here, and "off-topic" I see something worth mentioning. Looks like that right side water shutoff valve has been/is dripping. Also the hoses should be replaced with new, and with stainless steel braid.

Jim
WD5JKO

[KM1H]

The only way to tell the age is by the first 3 digits of the serial and then find a manual with that production run as they are all dated.

The early ones had Bumblebee caps, then Black Beauties for several years, then those ceramic cased El Mencos for a very short time, next Mylar, and next was a mix of mylar and disc ceramic and finally mostly disc and a few high value Mylar. Production spanned 1952-68.

That radio was built with Black Beauties and likely mid-late 50's. The ElMenco were either done at the factory during service after the factory discovered the problems with the earlier caps and before they had Mylars to use, or by an owner as well as all the ceramic caps which the the factory didnt use until the late 50's-early 60's and only with Mylars.

Remove the .1/600V from the rectifier plate pin as well as the AC line bypasses.
Pull the rectifier and then power up slowly with a variac or use the dim bulb method. That transformer could possibly be rewound for about half the price of a new one.

The transformer is an early one and soon replaced with the more traditional type with exposed laminations and a sheet metal top hat. New England Transformers were also in early NC-183D's and were hot running and failing junk.

Carl

[W1DAN]

Hi:

I actually think it may be one of the later HRO-60's, because you have the big tuning cap gear-box set screw on the rear of the gear box. I think (??) that the earlier HRO-60s did not have this. I always thought the potted power transformers were the later ones and were an engineering mod to reduce field failure rates. The secondary resistance of the transformers with the steel covers screwed on (with the NC logo stamped on it) were about double the potted ones. They got hotter and failed earlier (maybe Carl can confirm or deny all my ideas as I never worked at National?).

Either way, the 0.1uf cap from B+ to ground should be replaced or removed. I also put a 1 amp slow blow fuse in place of the 2 amp slow blow for the AC line in. I then add 1/4 amp fuses on each side of the secondary in case anything on the B+ line shorts.

Sometimes date codes of the tubes or a date code on the filter cap may provide a clue to the radio's date of manufacture, but Carl's idea or mating to a manual is a very good one.

Good luck and keep us posted on your progress!

73,
Dan
W1DAN

[n2len]

Thanks for the replies! I quickly snipped the .1 600Vlt and the AC Bypass caps....Removed the recifier and slowly brought it up on the variac....after 4 hours at 75 volts the transformer started to crackle. Like the was was cooking in the casing. Maybe a winding shorted?

[W1DAN]

Yes...

Most probably as you now only have tube filaments as the load.

Please re-read my earlier post as I made some corrections.

Dan

[n2len]

Thanks Much Dan...

Looking at the specs of the transformer has several taps...

PR) 115/230 VAC 60 HZ 1 PH
S1) 550 VCT @ 100MA CCS
S2) 5.0 VAC @ 2A CCS
S3) 6.3 VAC @ 6.5A CCS
S4) 7.5 VAC @ 0.45A CCS

Hammond manufactures a similar version missing the 7.5 Vac tap that is a replacement for the 50T...Digikey lists it for $88.00.

http://www.digikey.com/scripts/DKSearch/dksus.dll?Detail&itemSeq=120145428&uq=634842717875975841
Guess I can add another smaller transformer for the 7.5 vlts...

[KM1H]

As I said earlier the ONLY way to date it is by the first 3 digits of the serial which is the Engineering Run number. It is located on the far right edge of the chassis about midway.

The presence of the Black Beautys automatically tell me it is not early or late but around the middle as I also said earlier.

One addition/correction from earlier is that the earliest runs had the pink Sprague plastic sealed paper caps. Another is that some low value discs were used from either the beginning or soon after; however the Z5V designation shown in the photo wasnt used until several years later once standards were established.

I was also bassackwards about transformer styles, exposed laminations came first.

The presence of the El Menco of the same values as some of the BB's leads me to believe they were done later at the factory or an external location as National discovered that Sprague, Bumblebees and BB's were failing early; they kept changing but it didnt help. There is also a chance that they mixed the two brands in that run but that was generally not the rule. They didnt switch to the brown or maroon radial lead mylars until maybe 59-61. There will be a run or more that had all El Menco between the BB and Mylars.

My ER 345 was built between 1952-54 based upon evidence when I rebuilt it and has the exposed laminations with the top hat and no NC embossed (an obvious cost reduced step) and no SA 9209 stamp on the cover, is original and runs cool. It does not have the later tuning drive.

I pretty much give up on IDing these radios by things like transformers and tuning assemblies alone as both were regularly changed out in the Service Dept during my years there, 1963-69.

I do know that an enclosed style transformer was used as a NC-183D replacement by 1955 but the NOS one I have has no Manufacturers name. Those manuals used SA:5649 at the beginning and went to S461-1 later. It is my belief that the first change to the S461 (I dont have a manual with that version) was strictly a cost reduction and the S461-1 was its heavier duty replacement.

Im going out on a limb by guessing that the S515 shown in the photo and the S-515-1 in a later manual follow the same history. It could also be the difference between a part and drawing number now that I remember some of Nationals very confusing system which changed with management it seems.  Note also it has a NET choke.

Once a run # is known I might refine the build date a bit closer.

There are 3 secondary windings. 5V, B+ and a internally connected tapped winding that provided the 6.3V to all but the oscillator between terminals 1-2, and all in series to terminal 3 which fed the 4H4C current regulator. Its actually listed as 6.3-0-7.0V. There are SS regulator circuits posted on the internet to replace the 4H4C. If I was using a replacement transformer without that winding Id use the 6.3V, rectify, filter and Zener as the simplest way out. It provides voltage but not current regulation which is a minor point for normal use. Id also regulate the 2nd conversion oscillator filament.
The voltages you listed are for the original and the 100ma is quite a bit light.

Carl