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 Hotpoint L55FE with strange modification
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 Return to top of page · Post #: 1 · Written at 7:26:37 PM on 14 January 2018.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 505

Hi folks. I have recently acquired a Hotpoint which GTC correctly identified ad a model F55FE. It has the usual valve lineup with an extra

valve which shouldn't be there!

The usual 6J8G 6SK7GT 6SQ7GT 6V6GT 5Y3GT are all there yet there is a little 6BE6 behind one of the cans, wired up with a little tag

strip underneath. When the photo's come up you can see it, but what for and why is the question??? I'm not sure when I recap and check

resistors whether to keep it or take it out as it's certainly not original. Hmmmn???? Any ideas welcome...

Hotpoint L55FC
Hotpoint L55FC
Hotpoint L55FC
Hotpoint L55FC
Hotpoint L55FC
Hotpoint L55FC


 
 Return to top of page · Post #: 2 · Written at 8:45:36 PM on 14 January 2018.
Gfr53's Gravatar
 Location: Harston, VIC
 Member since 28 February 2009
 Member #: 442
 Postcount: 145

Hi Jamie,

The 6BE6 and the 6J8 are mixer/oscillator type valves. Is the 6J8 still wired up to the 1st IF transformer and to the oscillator coil/antenna input coil?.

Maybe a replacement due to a 6J8. being unavialable?

Cheers, Graham...


 
 Return to top of page · Post #: 3 · Written at 11:27:54 PM on 14 January 2018.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3859

A myriad of possibilities: It was rare but a pentagrid followed by a pentagrid did happen, however, his is a hack or a mod. 6BE6 I believe is closer to 6SA7 and neither valve, I would prefer on SW

Being SW 6A8 was superseded by 6J8. With varying issues (sometimes none) I have found several of the pentagrids like 6A8, 6J8, 6K8, ECH35 in the others hole. So that's a weird mod well away from era.

This has to be reverse engineered wholly & solely to try & work out out what that 6BE6 is doing? It is plausible that it replaces 6J8 oscillator, but normally you would change the socket, or use an adaption. It may be used as just the oscillator as you would with 6SA7, which, having no true oscillator grid, is recommended to have a separate exciter.

If it was not a lack of a 6J8? I would go through the Mixer section with a toothpick & comb. Two principal things predominate in killing that stage. One is the valve running out of emmision etc. and dying at High frequency and the other, it running out of volts. Pentagrids love lots of volts. The latter is normally due to those (serviceman types) who only changed enough bits to get it to run.

I have already had a HMV in the last few months where dodgy second hand parts were used and mistakes made. However, it was quite clear that the resistors had not been checked as several got relocated into my bin. The old laminated open type MIca caps in AWA / Hotpoint are of a type I have never needed to replace.

This is all interesting: These hacked sets and the ones that refuse to go, are the fascinating & educational ones.


 
 Return to top of page · Post #: 4 · Written at 12:06:47 AM on 15 January 2018.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5341

Note that Jamie says the 6BE6 is an additional valve. If his photos show how it's connected to the existing circuitry its raison d'ĂȘtre may become clear.


 
 Return to top of page · Post #: 5 · Written at 12:26:07 AM on 15 January 2018.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3859

Precisely why it needs reverse engineering:

Is the 6J8 still wired?
Is the 6J8 partially wired?
Is the 6BE6 fully or partially the mixer /oscillator, or something else?

Only one way to find out...........Pentagrid does not have to be a Mixer oscillator. 6BE6 was ruggedised & used in computers.


 
 Return to top of page · Post #: 6 · Written at 7:50:39 AM on 15 January 2018.
Johnny's avatar
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 335

Could even be a SW or LW home added converter.
JJ


 
 Return to top of page · Post #: 7 · Written at 8:34:35 AM on 15 January 2018.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3859

It may also be a BFO,a strait out amp, or a second mixer as a double conversion? The underlying missing and crucial link is its circuit and how it is applied?

It would not need to track if it is bringing in a fixed frequency like IF & spitting out another.

MBVC


 
 Return to top of page · Post #: 8 · Written at 8:42:50 AM on 18 January 2018.
Wa2ise's avatar
 Location: Oradell, US
 Member since 2 April 2010
 Member #: 643
 Postcount: 730

I did a mod to an All American 5ive AM radio to make it into a double conversion SW set.
See my web page here
It now has two pentagrid converters.


 
 Return to top of page · Post #: 9 · Written at 10:57:32 AM on 18 January 2018.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1345

That sounds like it.

Can we see some underchassis pics? Nice and close and clear?


 
 Return to top of page · Post #: 10 · Written at 3:17:04 PM on 18 January 2018.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 505

I've emailed photo's four days ago, is there a way now of uploading them?


 
 Return to top of page · Post #: 11 · Written at 5:24:20 PM on 18 January 2018.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 5624

JamieLee,

The photos went up last night however it may be that I've put them in the wrong thread. I will check things out when I get home and make corrections.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 12 · Written at 6:11:34 PM on 18 January 2018.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1445

Is this the wooden hotpoint version of the eggcrate. If so would you like photos of the under chassis of mine for comparison ?


 
 Return to top of page · Post #: 13 · Written at 10:06:40 PM on 18 January 2018.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3859

I have issues resulting from those photos. Its an incomplete refurbish, so its still do not power.

I have never replaced one of those rectangular AWA mica caps, however the cylindrical ones tend to crack, snap & short. These are also wax paper. Those Aerovox caps also have to go. Watch those caramel polyesters, I have seen some do what the black ones do.

Now isn't that little thing with 403 026 02 on it Indicative of "Confucius say picture is worth a thousand words". That thing should be in Transistor set so I wonder at its flash over? But its London to Brick, that that is an IF transformer. Fully consistent with a probable double conversion.

Now we need evidence: To see if its fixed or variable tuning or another IF. You now have something to compare it to.

Marc


 
 Return to top of page · Post #: 14 · Written at 10:22:51 PM on 18 January 2018.
JamieLee's Gravatar
 Location: Clare, SA
 Member since 27 March 2016
 Member #: 1894
 Postcount: 505

Thank you Brad, very much appreciated. No carl, I haven't got to that one yet, I'm still hunting a 6" electrostatic speaker for the eggy, this is a new one I was watching on gummie in the Adelaide hills. Price dropped to $60 so I lost all sense of control and bought, my brother lives in that neck of the woods and grabbed it for me. He wants me to do one up for him and put a Bluetooth thingy innit for him as ha doesn't listen to the radio. This has a phono input, so I could plumb it in there, which is my plan when I give him a suitable valve radio although since pulling this one apart I've realised it has like four shortwave bands, so if I get all that working he's not getting it, I'd rather give him a thumping console with a 75 & 42 and wire a jack with shielded cable in the back of the radio straight to the top cap of the 75 so when he plugs in his Bluetooth or thingy its a thingy but when not it's still a radio. I don't like Bluetooth, or going to the dentist! But with this one picture 5 & 6 show the hack board and valve socket. The blurry one shows the rest, yes it's blurry but the general idea it shows is everything looks wired up as original with hack added in. The mustard cap on the left of the little board goes absolutely nowhere and the little coil has only one side, 2 out of 4 terminals in use and the one on the left you can see has broken. Strange thing about this is it's strange... Can't figure out the purpose unless it's some kind of hack to over-ride a failure? As stated Marc, Johnny etc. Or maybe some kid got stoned and started soldering bits in to see what happens? Should be easy enough now I have the schematic, to snip out very cautiously and re-cap and measure resistors, then valves...


 
 Return to top of page · Post #: 15 · Written at 8:50:03 AM on 19 January 2018.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1345

OK, I did a quick trace of that circuit. What you have there is a 2nd mixer, to make the radio a double conversion set. Very much like Wa2ise's circuit, except not crystal locked, as far as I can tell. That little PCB type coil is from a Toko sample kit and it sets the 1st IF frequency.

From the components used it was done in two stages, late 1960s with further modification in the mid 1970s. Looks like whoever did it knew what he was doing. It should have worked quite well on short wave.

If you want to do a restoration and put it back to original, that shouldn't be too hard. Just pull out all the modern parts.


 
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