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Old 6th Jan 2020, 10:59 pm   #1
IsquaredR
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Default Hammarlund HQ-180A I.F. Help Sought

I've been restoring a Hammarlund HQ-180A and run into a snag. After replacing the resonance capacitors inside of IF transformers T3, T4 and T5 the receiver is dead. I've double-checked the wiring to each of the inner IF can coils and they are fine however I've discovered an oddity with the B+ voltage being fed to the 455 kc Gate (V17 6BA6) and the 1st Converter (V3 6BE6). While the plate voltage on these two tubes is supposed to be 250 volts DC, it is only 140 volts DC. The voltage coming from the OA2 is good (around 270 volts DC) and the plate voltages on all the other tubes are correct. My problem seems to be in the circuit vicinity of I.F. transformer T3.

There are two red wires going to T3's center pin (Pin "B" on my photo) that measure 270 volts DC; ostensibly this is the B+ input to the transformer. BUT yet the voltage being fed from the T3 (Pin "D" in my photo) to both plates of the 6BA6 and 6BE6 is only 140 volts DC.

Here's another anomaly of transformer T3: Pin "B" has NOTHING connected to it inside the can! Obviously either something is missing or it is simply an unused pin and Hammarlund used it as a tie point. Using the pin as a tie point makes no sense because a straight piece of wire would have been more logical. If there was any tap or coil inside the can connected to the pin with the red wires I would assume that the coil had opened, shorted or developed a high resistance internally. But there is nothing connected to that pin inside the metal can. Perhaps there might have been a short jumper that is not present on my T3 that connects the tie-point pin to Pin "D" (on my photo) which is then fed to the plates of both V17 and V3. But I have no such jumper.

By the way there also appears to be a schematic error with the tap for the B+ voltage for tubes V17 and V3 coming off of a grid bus instead of the B+ bus which feeds the other tubes.

I would be grateful if anyone has their HQ-180A on their workbench and would kindly compare my diagram of the underside of T3 with theirs. There may have been something omitted on my T3 that would account for the plate voltage drop from 250 VDC to 140 VDC (such as a jumper wire between two of the pins on T3. My diagram shows all that is found on T3.

Any help appreciated.
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Old 6th Jan 2020, 11:40 pm   #2
Skywave
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Lightbulb Re: Hammarlund HQ-180A I.F. Help Sought

I suggest that you measure - and make note of - the resistance between all the combinations of any two pairs of pins on T3. (I make that a total of 9 pairs). And then report your findings here.

Incidentally, I did try searching the 'Net for the schematic for this radio: not common. What is free is unreadable. Some are available though - at a price.

Al.
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Old 7th Jan 2020, 3:56 am   #3
IsquaredR
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Hello Al and thank you for your suggestion.

I have measured the resistance between all of T3's pins and will delineate them as per the letters on my photograph that is attached to my original post. The resistances are as follows:
A to B: Infinity
A to C: Infinity
A to D: 7.5 ohms
A to E: Infinity
B to C: Infinity*
B to D: Infinity*
B to E: Infinity*
C to E: 8.2 ohms
D to C: 3.5 ohms
D to E: 2.4 ohms

* The "B" pin is the pesky one that appears to NOT be connected to anything internally so obviously the resistance is whatever the ether will bear.

Finding a good clear schematic of the HQ-180A on the Internet is difficult so I scanned
the schematic from my original manual. Due to the size I uploaded it to the following links:

https://ibb.co/K2swJDW
https://ibb.co/WkPyFdV
https://ibb.co/qrGJ2y3

I provided a scan of the left side, right side and a composite of both sides put together. Unfortunately the left side view cropped a little of the far left and I will try to rescan it when I am near a scanner tomorrow.

Appreciate any and all help.
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Old 7th Jan 2020, 2:32 pm   #4
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Question Re: Hammarlund HQ-180A I.F. Help Sought

Thanks for your prompt response, re: resistance measurements.

Unfortunately, your readings - which I am sure you took care in making - appear to be inconsistent.
1. From C to D = 3.5 Ω.
2. From D to E = 2.4 Ω; from E to C = 8.2 Ω
Therefore, from 2: D to C = (D to E) + (E to C) = 2.4 Ω + 8.2 Ω = 10.6 Ω.
But that is inconsistent with 1: C to D = 3.5 Ω

Perhaps I've missed something: thoughts from other members may be helpful on that point. What type of instrument did you use for those resistance measurements? DVMs, when used to measure resistance of inductors, (especially if any capacitors are involved) can give misleading results; analogue meters are preferable for that reason.

As for the cct. diags. you listed, for me, the print is far too small to be of use: sorry.

Al.
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Old 7th Jan 2020, 2:52 pm   #5
Alistair D
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Page 78 of this version of the manual zooms in OK.

https://www.americanradiohistory.com...und-HQ-180.pdf

Al
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Old 7th Jan 2020, 3:41 pm   #6
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Arrow Re: Hammarlund HQ-180A I.F. Help Sought

Thank you, Alistair: that is a great help.

Looking carefully at that dwg., things are now a lot clearer. In essence, there are two coils: pri. & sec., with no d.c. connection between them. So, one pair of terminals is for the pri., but three terminals for the sec., two of which are internally joined. With that information now gleaned, it seems to me that when you replaced the capacitors across the pri. and sec. of T3, you made a wiring error of T3's internal connections to its 'outside world'. Note that the cct. diag. clearly shows that there are external connections to all five terminals of T3, which is not what you now have.

HTH,

Al.
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Old 7th Jan 2020, 3:44 pm   #7
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Default Re: Hammarlund HQ-180A I.F. Help Sought

With those readings I would have a close look at the 9pF cap C153.
Terminal B looks like it is used as a convenient loop for the HT perhaps (Red wires)
Don
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Old 7th Jan 2020, 4:27 pm   #8
IsquaredR
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Thank you very much Al and Don. The "red wire" middle pin is what has been bothering me so I know now that I need to find (or fish out of the coil) a missing lead. As for the resistance measurements, they were taken out of circuit (although with the resonance capacitors in place) and with a Fluke 8060B DVM.

I'll report back here as I go.

Thanks again.
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Old 7th Jan 2020, 5:44 pm   #9
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Arrow Re: Hammarlund HQ-180A I.F. Help Sought

The basic config. of T3 as an IFT is quite standard. But in this case, it seems as though a re-build of it to suit the surrounding circuitry is in order. I would approach that task in the following way . . .

1. Identify the primary and secondary windings.
2. The cct. shows the 'lower end' of each winding as decoupled to gnd. (C17 and C15).
It will be important to arrange the phase relationship between pri. & sec. so that the capacitive coupling between them is a minimum. It is usual for that to be so, so that the coupling, pri. to sec., is predominately inductive.
3. Connect the appropriate wires from each coil (4 + 1 in total) to tags on T3 such that those tags selected are conveniently adjacent to the wiring / components in the circuitry around T3. (It obviously matters not if the selected tags are not the same as those originally used. It's the electrical connections that matter; the physical arrangement as to whatever is convenient).
4. Fit T3 to the chassis and wire it in.
5. Check - using an Ohm-meter - that the connections now 'make sense'.
6. Apply d.c. power; check for correct d.c. voltage on V3 anode / plate.
7. Use your sig. gen. to adjust the alignment of T3 as required.
8. Finally - come back here and ask for further help, if you then find that things 'aren't right'!

And the best of luck - it usually helps!

Al.
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Old 7th Jan 2020, 8:19 pm   #10
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Default Re: Hammarlund HQ-180A I.F. Help Sought

If you were reading the resistances with the transformer out of circuit and C153 is not mounted within the can then it probably isn't that.
However, it looks like the primary is between C and E and the secondary between A and D. I think you should be getting an infinity reading between D and E. and A and C but I can't see why you are not getting a low resistance between A and C as well.
Unless there are other components mounted withinn the can then only four connections are needed. I't's not uncommon for unused pins to be used as convenient terminals.
I'm not familiar with this receiver so I'm quite happy to be corrected on anything I've said.
Don m5aky
By the way the 0A2 is a 150V regulator looks like the plate of V3 is fed from that.

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Old 7th Jan 2020, 11:33 pm   #11
IsquaredR
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Quote:
Originally Posted by Skywave View Post
Perhaps I've missed something: thoughts from other members may be helpful on that point. What type of instrument did you use for those resistance measurements? DVMs, when used to measure resistance of inductors, (especially if any capacitors are involved) can give misleading results; analogue meters are preferable for that reason.
No Al, you certainly didn't miss anything; it was purely "operator error."
I rechecked the resistances with both a 20000 ohm/volt Simpson 260 and an HP 410B VTVM and A to D read 8.4 ohms, C to E read 9.2 ohms and C to D was infinity.

I have examined the primary and secondary with a loupe and can find no evidence of another lead for that missing pin "B" feed. I am getting a strong feeling that there is a missing connection to the "B" pin. I also have observed that there is supposed to be a 1 K ohm resistor in the B+ feed to the coil which ends up providing 250 VDC on the plates of V17 and V3. There is also supposed to be a 1 K ohm resistor going to the B+ feed for transformer T4 which feeds the plate of V4. But (as you can see on my hand-drawn diagram of the underside of T3) there exists only a single 1 K ohm resistor that goes from pin "A" of T3 over to T4. I may be terribly mistaken but it seems like there should be two 1 K ohm resistors, one for T3 and the other that exists for T4. Perhaps I am missing one of them. Maybe once upon a time there was one going from pin "B" over to pinpin "D" which would supply the B+ voltage to the plates of V17 and V3. But I am fearful to rush in there and cobble together such an addition because I still wonder from where the 140 VDC on the plates is originating.
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Old 8th Jan 2020, 2:17 am   #12
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Just a quick one for now, since here in the U.K. it's early morning and I should be in bed! But I do love solving mysteries like this. Besides, the HQ-180 is a super RX.

In your opening post, picture #2, is shown a 1 kΩ resistor (R12) feeding T4. However, looking at the cct. diag., that is incorrect. The cct. diag., shows that 1 kΩ is connected to the B+ line. It feeds connection c on the coil (your drawing), thru the primary of T3, out on e and thus to V3 / pin 5 (plate, 1st. conv'r.) & V17 / pin 5 (plate, IF gate). The sec'y of T3 has d to the grid of V4 (IFA) and a to a green wire - which is probably AGC - R13, grid leak for V4, and R17 - probably AGC decoupling.

The coil pin b appears only to be a convenient tie-point for probably B+ (since the wire colours are red).

So as things stand, the B+ feed to V3 and V17 plates is wrong - which probably explains why the voltages you measured there were incorrect.

Al.
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Old 8th Jan 2020, 3:27 am   #13
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Default Re: Hammarlund HQ-180A I.F. Help Sought

I've yet to work on my HQ180. It must have the same problem as yours, that is, very poor sensitivity for such a sophisticated receiver.
BTW, I'm in Wisconsin USA as well
Dave, USradcoll1.
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Old 8th Jan 2020, 4:15 am   #14
IsquaredR
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Quote:
Originally Posted by Skywave View Post
Just a quick one for now, since here in the U.K. it's early morning and I should be in bed!
Al, if ever there was someone who deserved a good night's sleep it is you because you've been holding my hand on this HQ-180A-thing all day. It's now 3 AM in Chard so I hope you're deep in REM sleep and enjoying a wonderful dream.

There are some things about this receiver that have bugged me since I bought it and I am coming to the conclusion that someone has worked on it before. But what I don't understand is that it worked "OK"---not like you'd expect it to...but, just "OK." Like USradcoll1 intimated, its sensitivity was poor and its passband filtering was awful. I tried to do a sweep alignment and could not get anywhere near a decent flattening of the sweep. The alignment was flaky even after doing the factory manual's stock-in-trade peaking voltage to a VTVM. I suspected the IF coils had something going on so I dug in to find a couple of the mica resonant capacitors were bad. I drew the diagrams of the underside before I did any IF can work so I am perplexed as to how the receiver even worked at all prior to my project with the 1 K ohm resistor feeding T4. But Al, your suspicion coincides with my suspicion that there should be a 1 K ohm resistor that is missing in that B+ line to V3 and V17's plate. I also wonder if (in the frenzied heat of the "battle") early-on in my work if I might have removed the second 1 K ohm resistor, set it aside, forgot about it or it dropped into an abyss in my work area never to be seen again. Anyway, I am toying with the idea of rerouting the B+ feed and see what it does. I'll report back here to Mission Control afterwards.

And Dave...neighbor...nice to hear from you. I've owned several HQ-180As over the years, all splendid performers but this one has been a disappointment. However I also am a firm believer that HQ-180As are good receivers so maybe this one just needs some corrective measures or perhaps a house-cleaning of work others have done on it.
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Old 8th Jan 2020, 5:32 am   #15
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Default Re: Hammarlund HQ-180A I.F. Help Sought

My receiver came from a "silent key" in the Milwaukee area. It also came with the matching transmitter that I never tried, as I don't have a license.
The receiver doesn't look like it was worked on. It must be the nature of the beast, that it has the same problem as yours.
Dave, USradcoll1 as usual!
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Old 8th Jan 2020, 12:40 pm   #16
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Just to correct a mistake in my previous post.
T3 primary is C and D with Pin C going to the 0A2 via R12 and the transmit /receive switch.
T3 secondary is A and E.
In which case you should get the low resistance readings between C to D and A to E and infinity between the other pins.
It is possible the T4 terminal connected to the 1K (R12?) resistor from T3 pin C is just looping through.
Sorry for any confusion.
Don
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Old 8th Jan 2020, 1:22 pm   #17
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Arrow Re: Hammarlund HQ-180A I.F. Help Sought

Quote:
Originally Posted by vosperd View Post
Just to correct a mistake in my previous post.
T3 primary is C and D with Pin C going to the 0A2 via R12 and the transmit /receive switch.
T3 secondary is A and E.
Don - No, I don't believe that you did make a mistake in your previous post.

Based on the measurements made by IsquaredR in post 11, a study of the schematic and other 'bits 'n' pieces' in this thread to date, the attached drawing shows my analysis.

Al.
Jan. 8, 2020
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Old 8th Jan 2020, 1:49 pm   #18
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Quote:
Originally Posted by IsquaredR View Post
I've discovered an oddity with the B+ voltage being fed to the 455 kc Gate (V17 6BA6) and the 1st Converter (V3 6BE6). While the plate voltage on these two tubes is supposed to be 250 volts DC, it is only 140 volts DC. The voltage coming from the OA2 is good (around 270 volts DC) and the plate voltages on all the other tubes are correct. My problem seems to be in the circuit vicinity of I.F. transformer T3.
So far as I can make out the anode voltages for V3 and V17 given in the manuals (the one in the link at Post#5) valve voltage table for the HQ180A are wrong, according to the schematic for the HQ180A the anodes of those two valves derive their supply from the OA2 stabilizer valve which stabilizes at 150 volts, that might account for your voltage measurement difference.

Lawrence.

Last edited by ms660; 8th Jan 2020 at 1:58 pm. Reason: extra info
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Old 8th Jan 2020, 1:56 pm   #19
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Arrow Re: Hammarlund HQ-180A I.F. Help Sought

Quote:
Originally Posted by IsquaredR View Post
Al, if ever there was someone who deserved a good night's sleep it is you because you've been holding my hand on this HQ-180A-thing all day. It's now 3 AM in Chard so I hope you're deep in REM sleep and enjoying a wonderful dream.

I've owned, used and repaired many comms. receivers in my life, but never an HQ180. But I did get the chance to use one about 50+ years ago - it belonged to a friend who, probably unknowingly, was largely responsible for steering me into a career in radio / electronics. He had an HQ180X - and its performance was superb and a joy to operate.

My current main RX is a Racal RA-17W: 500 kHz to 30 MHz continuous, triple conversion. Soon after I bought it - about 10 years ago - I fully restored it: was in quite a sorry state. Now works just fine.

Yes, I had a good sleep thanks. I had a bizarre dream: not sure if it qualifies as 'wonderful', though. I was walking on the top of the chassis of an absolutely gynormous HQ-180: all the I.F. cans were skyscrapers!

Cheers, Al.
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Old 8th Jan 2020, 2:35 pm   #20
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Default Re: Hammarlund HQ-180A I.F. Help Sought

Al
Yes you are correct.
My mistake was to reverse pins D and E on the original post. I assumed they went round clockwise from A to E.
I must have got it correct the first time but wrong when I rechecked it.
Your sketch should make it clear for IsquaredR.
Not sure at this stage what the resistance readings are. If there is still a resistance between D and E of 2.4 Ohms, as originally stated, that could be a problem.
Don

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