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Author Topic: BC-1004C Question  (Read 4546 times)
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WZ1M
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« on: May 05, 2010, 06:38:04 AM »

I just aquired a Hammarlund BC-1004C with the power supply. Before I dive into this project, Is this receiver worth the effort to bring back to life. As far as I can see, nothing has been touched or modified. Outside is pretty ratty but fixable. Inside is clean.
Regards,
Gary...WZ1M
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W3FJJ
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« Reply #1 on: May 05, 2010, 08:12:24 AM »

Got one here and it ain't no SDR, so better trash it.. Just kidding, what's not to like?
one of the most FB boat anchor receivers ever made for AM. Great audio, Great selectivity  stable and
sensitive. I say only down fall, is note very accurate dial read out..   GL- Chuck-W3FJJ

I just aquired a Hammarlund BC-1004C with the power supply. Before I dive into this project, Is this receiver worth the effort to bring back to life. As far as I can see, nothing has been touched or modified. Outside is pretty ratty but fixable. Inside is clean.
Regards,
Gary...WZ1M
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The Slab Bacon
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« Reply #2 on: May 05, 2010, 08:14:20 AM »

Got one here and it ain't no SDR, so better trash it.. Just kidding, what's not to like?
one of the most FB boat anchor receivers ever made for AM. Great audio, Great selectivity  stable and
sensitive. I say only down fall, is note very accurate dial read out..   GL- Chuck-W3FJJ


Yea, what he said! ! ! ! !  Grin  Grin
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w3jn
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« Reply #3 on: May 05, 2010, 08:17:13 AM »

One of the best ever for AM use!

Beware all the dangerous landmines - the standy terminals on the back carry B+, beware of those 10 terminals in the back, and the IF trimmers are also hot with B+.  There are a bunch of bypass caps hidden in the IF cans.  Easy to get out though.  Harder are the bypass caps hiding in the RF deck.

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KM1H
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« Reply #4 on: May 05, 2010, 08:40:29 AM »

I wouldnt use Super Pro and stability in the same sentence Roll Eyes  The military left them on 24/7 and even then had crystal oscillator kits made up especially for RTTY links.

BTW, anybody have a spare PS for one?

Carl
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« Reply #5 on: May 05, 2010, 09:06:47 AM »

I have its brother the BC-774 and I think it works great for AM. Nice full audio with plenty of tessitura.  Wink
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« Reply #6 on: May 05, 2010, 09:30:41 AM »

The only bad Super Pro I have run across is a BC-779 made by Howard-I traded it for a couple of Halli R-42 speakers.

 I have several Hammarlund sourced Super Pro receivers here including the low frequency, BCB, and high frequency versions and they make nice AM/CW receivers.  Anything Howard touched was pretty much "cost reduced" but sort of worked.  I have Howard 450 and 490 receivers awaiting restoration and they are some of the few rigs the UPS man didn't mind delivering Smiley  With Howard gear the metal tubes weigh about as much as the rest of the receiver.

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w3jn
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« Reply #7 on: May 05, 2010, 10:19:38 AM »

I wouldnt use Super Pro and stability in the same sentence Roll Eyes  The military left them on 24/7 and even then had crystal oscillator kits made up especially for RTTY links.

BTW, anybody have a spare PS for one?

Carl

There's an easy mod in the receivers forum of the Handbook section here, posted by W3GL to add a small N750 cap to cure that, Carl.

The audio and continuously variable selectivity make up for any small drift problems.
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WZ1M
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« Reply #8 on: May 05, 2010, 01:27:13 PM »

OK, i'm convinced. I did skip around in the external power supply and found all the electrolytics a little leaky. Chokes and transformer are fine. I appreciate the heads up on the stability but being from the old school, I love to chase signals up and down the band. Now, for a good manual. The one on Bama is ok but a little fuzzy on different pages. As for the B+ on the terminal's on the back, you aint doing things right if you haven't got bit.
Regards,
Gary...WZ1M
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Todd, KA1KAQ
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« Reply #9 on: May 05, 2010, 04:06:09 PM »

Didn't we discuss this at Deerfield, Gary? Hmm?  Wink

The 'drift' and other issues from the past have some validity, but if you check out this link, you'll have a far better understanding of why:

http://www.radioblvd.com/hammarlund_super_pro.htm

And as Johnny sez, there's a simple fix to make it minimal, especially for AM use.

I once dismissed these sets myself until Johnny and the HUZman convinced me to give them another try. Sure glad, too. The one you got looked unmolested, and repainting the panel will be a cinch since it's a WWII model with smooth paint.

Heed 'JNs warnings about B+ floating around. I think the last good hit I took was off the back terminals of my SP-100 when I reached around the back for something. It'll get yer attention!

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WZ1M
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« Reply #10 on: May 05, 2010, 04:09:54 PM »

Yes Todd, I remember our brief eyeball on this unit. I did get the cover off the receiver and its covered with the tropic green stuff. Does not look like anyone has been in it with there solder gun. I am going to try to bring this back to life but will take awhile as I am swamped with rewinds.
Nice to see ya at the fester.
Regards,
Gary...WZ1M
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« Reply #11 on: May 05, 2010, 05:05:18 PM »

I have 2 BC-1004 receivers.  They are a good basic AM foundation, but they have numerous problems in stock form.  However, with just a little work, these are some of the best AM receivers out there!

1) DO NOT use the internal audio system.  Pick off the audio from the wiper of the audio gain pot, and feed an external high fidelity amplifier.

2) Slow down the AGC a little by adding a capacitor across the AGC line.  Low frequency audio appears on the AGC line.

3) Make a simple modification to the IF bandwidth control - bend the tab back a bit, which will allow the cores to move a little further into the IF cans.  This will allow you to get a couple of extra kHz of IF bandwidth in the wide mode.

4) The IF is not 455kHz.  Many folks are messed these receivers up by trying to move the IF to 455 :-)

The skirt selectivity is faily poor, but I'm assuming you have another receiver for "battle" conditions.

Otherwise,  they're quite reasonable.

The ones I have are no longer tube receivers - I converted them to solid state.  The BC-1004 I my main high fidelity receiver.

Regards,

Steve


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CW is just a narrower version of AM


« Reply #12 on: May 05, 2010, 08:10:42 PM »

The internal audio on the Super Pro is old school. It is really an audiophile throwback with a push pull in an essentially class-A manner. Push pull class A gives the benefit of double the swing and very low distortion but at the high price of heavy Iron, heavy current drain and lots of heat. The stage bias is fixed and controllable with a tapped resistor bleed in a rarely seen manner. With a little clean up, the on-board audio is fantastic.   

In fact it would be hard to imagine and receiver with an audio system that approaches this. The interstage transformer alone is the size of an apache mod transformer. An R390A with a peanut tube audio system - sure an off-board amp makes sense, but a Super Pro?

Steve - Next you are going to want to solid state one of these beasts Smiley

Mike

* bc1004_schem.pdf (22.71 KB - downloaded 88 times.)
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w3jn
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« Reply #13 on: May 05, 2010, 10:28:09 PM »

Indeed - the SuperPro has probably the best sounding audio of any communications receiver, stock.  It's most certainly not 10-100,000 hz at .1% distortion, but you're not gonna do any better with ANY stock radio.
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« Reply #14 on: May 06, 2010, 07:08:14 AM »

Ah yes  Wink  I figured there'd be some discussion about how wonderful the BC1004 audio is  Grin Cheesy Wink

It all depends on what your definition of good audio is.  My definition is very flat within the audible range with low distortion.  The BC1004 does not qualify in this regard.  Having used a BC1004 since 1972, and having used the stock audio and then having used external audio with the same receiver, there is a big difference.

So, whether to use the internal audio or not depends on what you want.  It is absolutely true that the BC1004 has better audio than virtually any communications receiver out there.  Of course, that's sort of like comparing a reasonably good table top radio like a Grundig, to an old Victrola   Grin  The Grundig sounds better, but as compared to a modern solid state stereo with big speakers and high power - well, - you get the idea.

I've visited a great many ham shacks over the past 40 years.  It is very interesting to see shacks of folks who can transmit fantastic audio, but use receiving setups that might make 100 cycles in the low end on a good day - and some who have just plain BAD receive setups (audio wise) - high distortion with poor frequency response.

An 8 inch speaker in a small box hooked to a communications receiver just isn't going to cut it  Cheesy
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« Reply #15 on: May 06, 2010, 10:45:07 AM »

Quote
There's an easy mod in the receivers forum of the Handbook section here, posted by W3GL to add a small N750 cap to cure that, Carl.

The audio and continuously variable selectivity make up for any small drift problems.


The SP-400 had that TC capacitor.

In the mid 60's when I had a 779 and 1004 the finer details were unknown to all but a few, for all I know they may have been Howards! But they never stopped drifting.

While the audio had plenty of timber rattling bass to a 12" Halli speaker, using triode connected 6F6's in both stages was certainly passe by WW2. Switching to the SP-400 6V6 circuit may be mo betta. Or rework to the SX-42/62/88 circuit. I cant think of anything useful below 100-150Hz anyway on AM radio.

Carl

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w3jn
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« Reply #16 on: May 06, 2010, 02:37:43 PM »

Ah yes  Wink  I figured there'd be some discussion about how wonderful the BC1004 audio is  Grin Cheesy Wink

 It is absolutely true that the BC1004 has better audio than virtually any communications receiver out there. 

My point exactly.

I use a Sherwood stink detector driving a stereo amp with a subwoofer.  Pretty much flat in my range of hearing... using the service monitor as a source it recovers audio very well from 10 hz past 12K where I can't hear anyway.  Course add in QRM, static, etc. and it's rare indeed when I can open up the RX to full bandwidth and fully enjoy its capabilities.  But a winter Sunday afternoon on 3733 with a rock crusher like WB3HUZ, it's the cats ass.

Carl, I guess you've never heard me on the air when some Harleys drive by on Rt 27 behind my house  Grin
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« Reply #17 on: May 06, 2010, 02:50:05 PM »

Quote
Carl, I guess you've never heard me on the air when some Harleys drive by on Rt 27 behind my house 


You proved my point John Grin  Tongue

Carl
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Todd, KA1KAQ
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« Reply #18 on: May 06, 2010, 02:52:28 PM »

Course add in QRM, static, etc. and it's rare indeed when I can open up the RX to full bandwidth and fully enjoy its capabilities.  But a winter Sunday afternoon on 3733 with a rock crusher like WB3HUZ, it's the cats ass.

Thatsright!  Grin

I've got the BudPro SP-100 next to my bed where it serves AM 740 Big Band music duty on Sunday nights. It drives an old 12 or 15" Jensen coaxial speaker in an EV enclosure. Sounds marvelous. No, I wouldn't use it for corntesting or anything but casual SSB listening, but then it's not a SSB receiver. It's an old radio. For a mid-30s design, I've yet to find anything that can touch it. And I have no desire to try to make it into something it isn't.

Now, if the cats start bitching about the audio being crappy, I'll have to give it some serious thought. They still hear pretty well. >^..^<

Bet that Meissner you have would give it a run for its money, John. Heard the one at Larry NE1S' place driving a large single cone speaker when I was visiting, HUZ and INR sounded like they were in the basement with us having a brew.

You have a keeper there, Gary. So what if it's not a new Yaecomwood? It's better.  Wink
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w3jn
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« Reply #19 on: May 06, 2010, 11:30:41 PM »

I'm reluctant to promote the audio in my Meissner TrafficMaster because stock, it doesn't have an output transformer.  I nabbed one out of an old HIHIFI amp with ultralinear taps, and wireed it up as such and added a little negative feedback.  Yep, it sounds absolutely fabulous - but it ain't quite stock.
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« Reply #20 on: May 07, 2010, 11:22:29 AM »

Interesting. Never knew that about the Meissners. Then again, I've seen exactly 2 in my life, and yours was one of them. Wonder what NE1S uses in his, or maybe it's a different model? I just recall it sounded clean and very HiHiFB in the fidelity department.
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« Reply #21 on: May 07, 2010, 12:05:24 PM »

I cant think of anything useful below 100-150Hz anyway on AM radio.


I can't speak to AM broadcast - there are so few music stations.  740 is pretty good :-)

But, on ham radio, there's stuff down there!  I was talking with Dave W9AD, and noticed immediately a change in his audio.  There was a real low end!  Dave got a new audio processor and stopped using the Optimod.  Turns out the Optimod (the one Dave was using) has a built in, non-switchable low cut below 50 Hz.

I noticed the difference immediately, unsolicited.  "Dave, did you do something with your audio?  I hear low end response I never heard fromyour station."

Sometimes there is response below 50Hz :-) 
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« Reply #22 on: May 07, 2010, 02:29:29 PM »

There is a fair amount of AM music on the BCB and SW. I only listen to 740 on Saturday evenings to the old R&R, the Beverages help dig a lot of others out. Too bad 940 went under, they had more hours of my sort of music. The AMBCB is where the real lows have a purpose when the signal is decent

I didnt say that there was nothing in the rumble area of the spectrum, just nothing useful IMO on the ham bands which is what I meant earlier. Id rather quit wasting power down there and get a lot more power out of old BC iron by rolling the lows off. Then emphasizing high positive peaks. My goal is to communicate, not sound like a pampered preacher.

Carl
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« Reply #23 on: May 07, 2010, 05:01:13 PM »

I didnt say that there was nothing in the rumble area of the spectrum, just nothing useful IMO on the ham bands which is what I meant earlier. Id rather quit wasting power down there and get a lot more power out of old BC iron by rolling the lows off. Then emphasizing high positive peaks.


Even using a series modulator, as I do, it takes a LOT of power away from the capabilities of the station when you have the 'rumble freq's' passed.

I can see about 15 to 20 percent MORE PEP when I turn the subsonic synth OFF in the mobile.


--Shane
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N3DRB The Derb
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« Reply #24 on: May 08, 2010, 01:02:38 PM »

The last AM'er playing swingin kool music near Johnny and I is a KW out of Hagerstown MD, WJEJ on 1240. All locally generated programming except for news feeds off a bird.

Here's a pic of their xmitter from B. Mishkind's website.  BC 1H, sounds wonderful on a good receiver.


* Gates-BC-1H.jpg (131.21 KB, 465x1035 - viewed 170 times.)
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