[Hammarlund] Replacing caps in HQ-129 and others

Sat Dec 26 12:23:22 EST 2009

I'll add another suggestion to Chuck's recommendations:

My HRO-50 had an intermittent paper capacitor connected to HV at the 
power transformer terminals.  It would short periodically, causing 
the power transformer to fail if the radio was not turned off fairly 
quickly.  It was not listed on the schematic, so was easy to overlook.

This is the second attempt to respond.  I neglected to add Hammarlund 
to the To: line on my first answer, and only sent it Chuck.  Here's his reply:

Hello jim.
I believe that this capacitor lies in the HRO-50-1, but not in the 
original HRO-50. NOT replacing this capacitor in this set before 
powering up equals a death sentence for the power transformer. This 
is a CLASSIC example of why these radios should be completely 
re-capped before applying ANY power. I have NEVER seen an HRO-50, or 
60 that was "OK' to power up in "as found" condition.
Chuck N1LNH

Chuck:
I think I have the basic HRO-50.  If I remember correctly, the HRO 
50-1 has the upgraded IF with a number of IF transformers in each 
stage, and I was disappointed later that I had not looked for 
it.  Before buying mine used in the late 50's-early 60's  I checked 
QST ads and the HRO-50 was the oldest HRO with the upgraded front end 
and direct reading dial.  However after doing some Googling, it 
appears that only a 3rd IF stage was added.  Am I correct about the 
extra IF transformers?  My receiver has miniature tubes in the RF and 
octal tubes in the IF.

Jim

At 11:06 AM 12/22/2009, you wrote:

>Hello all.
>
>Picked up the conversation about bad caps in an HQ-129, and have 
>some advice-for what it's worth.
>
>Here is how the pros do it:
>
>
>
>You should assume that any radio made prior to the early 1960's will 
>have ALL bad capacitors, even if, at first, things appear otherwise. 
>After that, makers turned to ceramic caps to a large extent, and 
>these seldom cause problems and should NOT be randomly replaced 
>(such as those found in HQ-180s). Going back a little further in 
>time we find radios like the Heath Mohawk(1958) that use paper caps 
>that have better plastic, and are probably OK, but at least should be TESTED.
>
>Before this point in time, we have the infamous "Black Beauties of 
>Death" and most of us know what that means!
>
>
>
>The capacitors being manufactured today FAR surpass their earlier 
>counterparts, and with careful selection, it is often possible to 
>"improve" the operation on boat-anchor radios, particularly in the 
>"stability" and "drift" areas.
>
>
>
>ALWAYS replace ALL of the old "paper" capacitors, whatever they look 
>like, and whatever condition they APPEAR to be in.
>
>
>
>Check ALL of the micas that look like chicklets.
>
>Own a reliable (digital) capacitor meter, or have some other 
>instrument on your bench that you can trust. Mica capacitors 
>should  ALWAYS be checked for both capacitance AND breakdown 
>voltage. For this, you will need a megger, like a hand-cranked 
>Biddle, or an electronic megohmmeter, such as a General Radio, or a 
>Freed. Often, it will be a better use of your time to just go ahead 
>and replace them. Use NEW silver-micas.
>
>If you  are into the front end a particularly difficult radio, such 
>as a Halli SX-28, or SX-62, just replace them ALL as quickly as you 
>can, and move on. You will REALLY be wasting your time if you have 
>to go back in there again!
>
>
>
>Electrolytics require a somewhat different approach. Small 
>electrolytics should be treated like "papers". Just replace 
>them-period. Can types are very hard to find (and expensive) these 
>days, although AES has many in stock. These should be tested in the 
>radio, and often they will be found to be OK. Re-forming may be 
>necessary, and the ones that are OK will, most likely, continue to 
>be so,  as long as the radio is used periodically. Often a judgement 
>call is required here.
>
>
>
>Resistors are a somewhat different matter. Own a decent digital 
>multi-meter. Check ALL resistors and replace those that have risen 
>over their specified tollerance ( 5-10-20%). In some cases, such as 
>grid bias resistors in PP audio stages, try for tighter tollerances. 
>It is often more important that they be MATCHED, rather than their 
>exact value be correct. Some radios, such as National HRO-50s and 
>60s, will require nearly ALL of their resistors replaced. This is 
>not a reflection on the radio, but rather the resistor manufacturer, 
>in most cases.
>
>
>
>Have the schematic with you on the bench, and, as you move along, 
>check what is on the schematic with what you see in front of you. Be 
>VERY suspicious of any previous repairs / parts changes. You can not 
>know what a previous tech was up to, and these parts may not be 
>correct, or even wired up properly. Again-use your schematic, and 
>the parts list.
>
>
>
>Always remove ALL of the old part leads from the tie points. Doing 
>otherwise is simply sloppy work, and will often come back to bite 
>you with intermittant connections, solder bridges etc.
>
>
>
>One other thing: Do NOT assume that, just because a component is 
>new, that it works as it should. Always test new capacitors and 
>resistors BEFORE installation. The small additional time that this 
>takes will pay for itself in reliability of operation, and 
>confidence in your work.
>
>
>
>Restoring boat-anchors is a very time consuming operation, and 
>requires skill, patience, and good practices regarding testing, 
>soldering etc. I restore radios for a living, and have been doing it 
>for decades. Long ago I learned that the time invested in this 
>approach pays off very well, and there is nothing like the feeling 
>that you get when you flip the switch, and EVERYTHING works as it 
>should. If this approach is NOT followed, you will pay dearly with 
>time wasted chasing down nasty little problems, such as those mentioned.
>
>Do it right, do it once. Move on and enjoy your radio.
>
>
>
>Chuck N1LNH
>
>East Bridgewater MA
>
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