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Hello to the group and thanks to the owner for allowing me to post.
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Today when visiting a Vintage wireless meeting, I picked up a battered Hallicrafters TW 2000 from the estate of a deceased member.? I would like to ask a few questions if I may, mainly on cosmetic items?
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The radio is missing the front wrap cover, which obviously did not help it as the radio had taken a big knock on the front brass bezel just on the writing of 'Dynamic Tuner' and this smashed the glass into several pieces, the brass has been straightened the best I can, and plan to use a piece of acrylic sheet to replace the glass.
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The plastic section at the bottom of the radio that has the wording of Band selector Tuning Off On Vol, has what looks like aluminium foil on the front edge, is this meant to be what is covering it or is this a replacement for something else already damaged.? Perhaps the picture below will help in this description.
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It is also missing the 'Skyrider antenna'. ? I am assuming that this is basically a copy of the internal ferrite antenna, but has a small trim cap rather than the 22pF and is fitted into a plastic tube with a few rubber suckers to stick on a window.
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I know it is not really needed, but if I get chance at some point I could always make up? a replacement so if anyone can confirm if it is the same I would appreciate it.
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Power has not been applied to the radio by me yet, I plan to replace the Hunts tubular paper caps and check the main smoothing caps before any power is applied.?
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Lastly, it has the Ballast Adaptor fitted to allow for 220 Volts AC and has already got a 240 Volt mains plug fitted so I assume the slightly higher voltages we have in the UK should not matter as it stands, I will build up a battery pack for it initially at 90 Volts and 9 Volts and when happy will remove the ballast and fit a 240 to 110 Volt isolation transformer, it should save on a bit of heat within the radio case.
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Cheers
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Adrian
G8UGD
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May as well post this here following on from my last.?
The radio is basically working but the IF section is not as expected.
The coils do not have any built in caps that I can see, and the cans will not tune down to 455kHz as it says it should be in the book. There is what appears to be a stiffener in the base of the IF assembly it has a rivet going all the way through, but appears not to have any electrical connection with the coils.? Thinking this is just to guide a trim tool
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The service manual does not show any external capacitance for the cans so I am assuming that it relies on a bit of self capacitance and that of the valves input/outputs to resonate.? I can get the IF's to peak at 530kHz, but one tuning slug is just on the edge of peaking.
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The other option is to add a few external capacitors.
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Just wondering on peoples thoughts on what I am finding?
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Adrian
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the 2 plastic squares are the bread and in between the caps are the meat.
On Monday, November 18, 2024 at 01:35:43 PM EST, Adrian Hodgson via groups.io <adrianh991@...> wrote:
May as well post this here following on from my last.?
The radio is basically working but the IF section is not as expected.
The coils do not have any built in caps that I can see, and the cans will not tune down to 455kHz as it says it should be in the book. There is what appears to be a stiffener in the base of the IF assembly it has a rivet going all the way through, but appears not to have any electrical connection with the coils.? Thinking this is just to guide a trim tool
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The service manual does not show any external capacitance for the cans so I am assuming that it relies on a bit of self capacitance and that of the valves input/outputs to resonate.? I can get the IF's to peak at 530kHz, but one tuning slug is just on the edge of peaking.
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The other option is to add a few external capacitors.
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Just wondering on peoples thoughts on what I am finding?
?
?
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Adrian
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OK thanks Bill, in that case having a closer look I guess they are some form of compression cap, but without seeing a way of re-adjusting them I am a bit stuck.
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Is there any way to stabilize them or remove what is fitted without destroying the plastic?
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Could the rivets have eased off over the past 60 + years. ? My little TC1 measures the coils as adjustable between 0.4mH and 1.1mH so they seem OK
I could drip some superglue into the cap area to try and stabilise/lock them from moving and then fit external caps, or I could replace the IF cans with some out of a typical battery valve radio?
Adrian
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Adrian??? Yaaa , ?Silvered Mica caps underneath; ?but out of tolerance that much? you say? ???the cans will not tune down to 455kHz ??… ?so ?It would seem the caps decreased in mmFds. ????? but? you also say? ?I? can get the IF's to peak at 530kHz, … ?so It would seem the caps increased in mmFds. But that is strange, how? ?? …so I am missing something I guess. Are all slugs moving ok? Do they all seem to peak near the same frequency? Thanks for the good picture of the IF can guts ?? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Bill Green via groups.io
Sent: Monday, November 18, 2024 1:52 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] Hello to the group, new member with a TW-2000? the 2 plastic squares are the bread and in between the caps are the meat. On Monday, November 18, 2024 at 01:35:43 PM EST, Adrian Hodgson via groups.io <adrianh991@...> wrote: May as well post this here following on from my last.? The radio is basically working but the IF section is not as expected. The coils do not have any built in caps that I can see, and the cans will not tune down to 455kHz as it says it should be in the book. There is what appears to be a stiffener in the base of the IF assembly it has a rivet going all the way through, but appears not to have any electrical connection with the coils.? Thinking this is just to guide a trim tool The service manual does not show any external capacitance for the cans so I am assuming that it relies on a bit of self capacitance and that of the valves input/outputs to resonate.? I can get the IF's to peak at 530kHz, but one tuning slug is just on the edge of peaking. The other option is to add a few external capacitors. Just wondering on peoples thoughts on what I am finding? -- don??? va3drl
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It seems to me that if the coils are adjustable, and it looks like
they have threaded ferite, its unlikely the caps are also adjustable.
One or the other, not both.
Since you can measure the inductance is it possible to measure the
capacitance also? Can you disconnect the two? Two reasons for this: one
is that you can calculate the resonant frequency range possible from the
capacitance and range of inductance; secondly, if the capacitors can be
separated from the coils via connections, its possible to substitute
external caps of the right value, assuming the internal caps have
changed so much the coils are out of range.
IF transformers with built in caps are fairly common. One problem
is that where silvered mica caps are used they can suffer from
silver-mica disease where the silver plating oxidized. Sometimes results
in shorted caps but often in large change in value and unstable
capacitance.
Note that all IF transformers are not the same: they are designed as
impedance matching devices and coils for one kind of tube or circuit may
not work well for another circuit, even if the resonant frequency and
coupling (which determines bandwidth) are correct. It is NOT one size
fits all.
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Show quoted text
On 11/18/2024 12:36 PM, Adrian Hodgson via groups.io wrote: OK thanks Bill, in that case having a closer look I guess they are some
form of compression cap, but without seeing a way of re-adjusting them I
am a bit stuck.
Is there any way to stabilize them or remove what is fitted without
destroying the plastic?
Could the rivets have eased off over the past 60 + years. ? My little
TC1 measures the coils as adjustable between 0.4mH and 1.1mH so they seem OK
I could drip some superglue into the cap area to try and stabilise/lock
them from moving and then fit external caps, or I could replace the IF
cans with some out of a typical battery valve radio?
Adrian
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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As I recall, many people have removed those? SM caps or disconnected them on typical ?IF transformers and added external ones, so it must be possible. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow via groups.io
Sent: Monday, November 18, 2024 5:24 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] Hello to the group, new member with a TW-2000? It seems to me that if the coils are adjustable, and it looks like
they have threaded ferite, its unlikely the caps are also adjustable.
One or the other, not both.
Since you can measure the inductance is it possible to measure the
capacitance also? Can you disconnect the two? Two reasons for this: one
is that you can calculate the resonant frequency range possible from the
capacitance and range of inductance; secondly, if the capacitors can be
separated from the coils via connections, its possible to substitute
external caps of the right value, assuming the internal caps have
changed so much the coils are out of range.
IF transformers with built in caps are fairly common. One problem
is that where silvered mica caps are used they can suffer from
silver-mica disease where the silver plating oxidized. Sometimes results
in shorted caps but often in large change in value and unstable
capacitance.
Note that all IF transformers are not the same: they are designed as
impedance matching devices and coils for one kind of tube or circuit may
not work well for another circuit, even if the resonant frequency and
coupling (which determines bandwidth) are correct. It is NOT one size
fits all.
On 11/18/2024 12:36 PM, Adrian Hodgson via groups.io wrote: OK thanks Bill, in that case having a closer look I guess they are some
form of compression cap, but without seeing a way of re-adjusting them I
am a bit stuck.
Is there any way to stabilize them or remove what is fitted without
destroying the plastic?
Could the rivets have eased off over the past 60 + years. ? My little
TC1 measures the coils as adjustable between 0.4mH and 1.1mH so they seem OK
I could drip some superglue into the cap area to try and stabilise/lock
them from moving and then fit external caps, or I could replace the IF
cans with some out of a typical battery valve radio?
Adrian
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
-- don??? va3drl
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What you have in the picture? is a typical IF that by the mid 50's is what virtually everyone used.? But before decide it's defective it should be in the radio circuit before you try an alignment.? The caps are fixed, the slugs are used to set to a predetermined frequency.? Older style, much larger used variable caps or trimmers.
You should do a google search for 'IF silver mica disease'.? Someone will tell you how to determine is the caps are bad and how to repair.
On Monday, November 18, 2024 at 03:36:06 PM EST, Adrian Hodgson via groups.io <adrianh991@...> wrote:
OK thanks Bill, in that case having a closer look I guess they are some form of compression cap, but without seeing a way of re-adjusting them I am a bit stuck.
?
Is there any way to stabilize them or remove what is fitted without destroying the plastic?
?
Could the rivets have eased off over the past 60 + years. ? My little TC1 measures the coils as adjustable between 0.4mH and 1.1mH so they seem OK
I could drip some superglue into the cap area to try and stabilise/lock them from moving and then fit external caps, or I could replace the IF cans with some out of a typical battery valve radio?
Adrian
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Hello Don, Richard and Bill.
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I am pretty sure that the base of the IF can where the caps are is flexing, or moving as I tune, if I put pressure on the cores I will see changes/jumps in the tuning, especially when monitoring the agc line.? So suspect that the caps are loose or intermittent.? They seem to be small plates with mica in between and suspect either because of age/heat or what ever that they are not being held as tight as they were in manufacture.
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I have a few options I guess, unsolder the fine wires from the terminals, this depends on my eyesight and how dexterous I can be in not breaking any wires in the process. Then remove the cap section, grind away the rivet and see what I find that I can then cut out. fit external caps as discussed, and refit.
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Or.
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As mentioned I do have some other IF cans from 1.4 Volt battery valve/tube broadcast radios, similar valves as in the DF/DK series, they may not be perfect matches but at present may prove to be a simpler alternative.?
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So I will try them in stead and keep the originals for a fettle possibly later.
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The radio cost me all of ?1 (1 UKP) approx $1.27 as no one else wanted it so apart from the glass and a few caps stands me at very little.? It does not seem to be a popular sought after radio.? I originally got it with the intention of parts! but decided to see if it would work.? I also doubt I would find the front cover.
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Don, as the IF would tune higher at around 530kHz it does point to the caps going less in value.
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From my workings out: -
If the coil/core fully in was around 1.1mH and only just making 530 kHz, it would suggest the caps, associated wiring and tube capacitance amounted to around 80 pf in parallel.??
If I work at mid range for the coil at say 0.75 mH and a frequency of 455 kHz, then the total capacitance I get should be around 160pF.
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That's just my rough calcs for how much pf,? is missing
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Another trying to be quik comment as Bills comment was only seen after I posted above.
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It looks like they are Automatic Mfg Co IF cans as described in ( hope I can post this link.) so there is a repair process I could try.
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Adrian
G8UGD
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I managed to break one of the wires to a coil on the original cores, so I went ahead with replacement IF cans. ?It is now working OK. ?The IF is tuned to 455 kHz and stays there and a run through of the tuning procedure and for the time being the radio is done.
Pic below of the replacement IF cans in situ, they do not look that out of place. So generally happy it is working and picking stations OK.
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Adrian
G8UGD
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Great news!? I've fought with these things in the past on S-38 and S-120 models.? Were you able to order these new or were they from a parts machine?
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73,
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Justin B.
KI5GKD
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Oh, on an S-38C I had very bad SMD? (sounded like I was in the middle of a severe thunderstorm!) and I wound up replacing the innards with a 455 KHz resonator and a couple of coils...
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73,
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Justin B.
KI5GKD
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The coils were from a scrapped part chassis I had, from a Vidor, My Lady Catherine Picnic Radio.
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It originally would have had DK96, DF96, DAF96 and DL96 valves, it would have been powered from a 90 Volt HT battery with a 1.5 volt battery for the filaments.
The IF originally would have been 470 kHz but the cores easily go down to 455 kHz.
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Adrian
G8UGD
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don Root