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Old 21st Jan 2018, 9:46 pm   #1
Darrencambs
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Default Blaupunkt Arkansas 43942 Restoration

Hello all,

I picked up an eBay bargain a couple of weeks ago. An Arkansas radiogram and Challenge radiogram for 26 in total (cost me more in petrol for the round trip from Huntingdon to Bradford to collect them).

The Challenge is beyond economic repair as it looks like it's been underwater - chassis rusted, chipboard cabinet disintegrating, legs fallen off; but the Arkansas looks to be in decent condition. The Challenge will be going down to the local tip (unless anyone here wants it for spares?), and I intend restoring the Arkansas.

I'm a novice at this, but have a reasonable understanding of electronics and a great deal of common sense around mains electricity. I've also done a great deal of reading of numerous posts on this website - so, thanks for all the help so far! I've got a copy of the schematic for a Granada 23400 which seems to be an identical chassis, albeit in a different cabinet.

Not much done yet apart from extracting the tuner/amp chassis from the cabinet and giving it a clean up (hoover and paintbrush), and having a nose around for any obvious problems. It doesn't look as though it's been meddled with in the past and the absence of a mains plug is encouraging as I don't think it's been used for some time.

Reading through the forum, I know I should change the output grid caps (two on this model, I believe - one for each ECL86) which I've circled in one of the attached pictures. There seems to be differing opinion on whether all wax capacitors should be changed... I'm sitting on the fence at the moment, and willing to listen to those with experience. Are there any other common problem caps on this model?

Although the chassis looks to be in original condition, I noticed two yellow wires to the left of one of the ECL86s looks to have been snipped. I have had a look online for pictures to confirm whether this is the case or not, but with no luck. I can't locate this on the schematic.

Finally, the mains transformer sits over a particularly large smoothing can. Given this can is, perhaps, older than I am, should I replace this as a matter of course? I imagine that could make quite a mess of things if it did go pop.

This won't be going anywhere near the mains until the crucial jobs have been done - including fitting a new 3-core mains cable - and I'll be building a lamp limiter too.
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Old 21st Jan 2018, 10:40 pm   #2
Edward Huggins
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Default Re: Blaupunkt Arkansas 43942 Restoration

Your bargain Arkansas looks in super condition. There's quite a lot of general info around on this very collectable model. As for the "Challenge", what type of Autochanger did it have?
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Old 21st Jan 2018, 10:55 pm   #3
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Default Re: Blaupunkt Arkansas 43942 Restoration

My opinion. Unless you have good reason to believe that capacitor can has failed (such as evidence of venting) I would leave it alone. Build that lamp limiter and it will probably reform and be fine.

Lovely looking piece of kit. Good luck with the resotoration.
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Old 22nd Jan 2018, 7:50 am   #4
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Default Re: Blaupunkt Arkansas 43942 Restoration

Welcome to the forum Darren, it's always a good ide to post a schematic if you have one, to help with the yellow wires for instance.

Definitely start it up on a lamp limiter and a variac if you have one whilst reading the HT (high voltage) on the big can/cap. If you have two meters use one as an ammeter; on the mains tfmr, there is a HT fuse, it can be taken out to measure the current on first start up. Re the big can/cap, in all likely hood, it will be fine for now, at least till you get everything else sorted. you can always change it later. There are a lot of smaller German made electrolytics in these, these can hopefully be checked with voltage readings.

Look after those ECL86's, they are rare, hard to get for reasonable money valves, worth more than what you paid for the two grams.

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Old 22nd Jan 2018, 9:55 pm   #5
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Default Re: Blaupunkt Arkansas 43942 Restoration

Quote:
Originally Posted by Edward Huggins View Post
Your bargain Arkansas looks in super condition. There's quite a lot of general info around on this very collectable model. As for the "Challenge", what type of Autochanger did it have?
Thanks Edward. It doesn't look too bad, so I'm hoping it will be quite straight forward. The cabinet needs a bit of TLC, but should come up nicely. More than can be said for the Challenge (pictures below) - which has a Monarch autochanger.
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Old 22nd Jan 2018, 10:29 pm   #6
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Default Re: Blaupunkt Arkansas 43942 Restoration

Clydeuk, Diabolical Artificer, thanks for the tips. The can does look OK as far as I can see, so fingers crossed. I don't have a variac, but have a handful of multimeters so connecting one as an ammeter will be no problem.

Re the schematic, attached is a copy of the service manual. Not the best quality. I have a better resolution version which I don't have to hand at the moment.
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Old 23rd Jan 2018, 6:56 am   #7
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Default Re: Blaupunkt Arkansas 43942 Restoration

Crikey, looks like it's been used for a party on the beach! you have your work cut out.

A
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Old 23rd Jan 2018, 10:33 am   #8
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Default Re: Blaupunkt Arkansas 43942 Restoration

That Ace "Challenger" has a BSR UA15 autochanger and a BSR TC8S stereo cartridge which might be worth saving. If you were gong to scrap it, I would be tempted to save the deck, the valves and both the OPTXs.
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Old 23rd Jan 2018, 8:06 pm   #9
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Default Re: Blaupunkt Arkansas 43942 Restoration

I would suggest saving the valves as well. If it were me I would save the chassis but I appreciate not everyone has space.
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Old 23rd Jan 2018, 8:19 pm   #10
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Default Re: Blaupunkt Arkansas 43942 Restoration

I wonder who actually made the Ace Challenger radiogram? I've seen that model wearing various badges. My grandmother had one for many years branded as an Argosy. I was fascinated by the illuminated display cabinet!

The Blaupunkt looks fantastic Darren. Good luck with it.

Steve
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Old 23rd Jan 2018, 8:47 pm   #11
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Default Re: Blaupunkt Arkansas 43942 Restoration

I think the Ace Challenge employs the STC G.C.6 chassis which is given in the 1966-1967 radio and tv servicing book
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Old 25th Jan 2018, 11:20 pm   #12
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Default Re: Blaupunkt Arkansas 43942 Restoration

Thanks for the replies, everyone. Apologies for the radio silence (pardon the pun). Been a busy week.

I left the Challenge in the back of my Shogun, but I will pull out the tuner and record deck this weekend and salvage what I can.

Plans for this weekend are to build the lamp limiter and a jig to hold the Arkansas chassis while I'm working on it. The last thing I want to do is damage any components while it's on the bench - I've built a rollover jig for a VW camper, so this particular chassis shouldn't pose too many problems!
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Old 11th Feb 2018, 10:42 am   #13
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Default Re: Blaupunkt Arkansas 43942 Restoration

Morning all,

Been a bit busy at work these last few weeks, but have made a small amount of progress on this project. Lamp limiter is built and I've knocked up a jig to hold the radiogram chassis.

I've attached a copy of the service manual (from a Granada 23400) and made a visual check of all the wax capacitors. All look OK with none showing any obvious signs of problems.

However, some of them are going to be a nightmare to get at without completely stripping the chassis down, so I'd be grateful for any opinion on which ones I should definitely replace before I start it up. I'd also welcome any recommendations as to the best brand, type and where to source the replacements from.

Thanks in anticipation!
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Old 11th Feb 2018, 12:56 pm   #14
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Default Re: Blaupunkt Arkansas 43942 Restoration

Before I start the replacement of any Caps, which should be section by section starting with the AF stages) I'd want to check out the insulation on that mains transformer which looks in very poor health.
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Old 11th Feb 2018, 1:25 pm   #15
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Default Re: Blaupunkt Arkansas 43942 Restoration

If that's the one in post 5, that's the Challenger which was scrapped, not the Arkansas.
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Old 11th Feb 2018, 4:03 pm   #16
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Default Re: Blaupunkt Arkansas 43942 Restoration

Edward, Bill,

Thanks for your replies.

That mains transformer pictured is indeed the one in the Challenger. I've salvaged the valves and autochanger from that one and the rest of it has been scrapped. I'll post up a pic of the Arkansas transformer later which, to my eye, doesn't look to be in too bad shape.

In the meantime, I've been having a poke around and pulled out one of the capacitors (C748 on the schematic) which was sitting beside one of the ECL86's. According to the multimeter it reads OK.
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Old 11th Feb 2018, 4:20 pm   #17
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Default Re: Blaupunkt Arkansas 43942 Restoration

That's a polysomething capacitor, so is almost certainly OK. It's the old paper insulated ones, from any manufacturer, that are generally duff by now. Chances are that they're all OK, with the possible exception of any mains filters.

A quick and dirty check on "that capacitor" is to measure the cathode voltage on pin 7 and quickly short the triode anode (pin 9) to chassis. The voltage shouldn't move significantly.
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Old 13th Feb 2018, 11:52 pm   #18
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Default Re: Blaupunkt Arkansas 43942 Restoration

Thanks for the tip Bill. I've read about that but, this being the first time I've worked on a mains powered valve radio, you will understand I'm approaching this with a degree of caution so need to be 100% sure I'm shorting the correct pin.

I've taken half a dozen or so of these caps out of circuit and checked them. All are showing +/- 10% of labelled values, and none are showing any leakage under the meter (not checked at operating voltages though as I don't have the kit for that).

I've replaced the mains cable with a 3A three-core. I've not yet made my mind up about earthing, but I think I'll leave it disconnected for now.

I have ordered some replacement grid coupling caps (22nF / 630V, whereas original were 450V) but, having done a bit more research, the original WIMA ones do appear to have a decent reputation for longevity, so I am tempted to keep them and preserve the originality.

The Granada schematic appears, to me, to be the same as the layout for the Arkansas - albeit minus the socket for the autochanger, and I haven't spotted any mains smoothing caps but will have another look this weekend.

My main concern is the big can that sits under the mains transformer. The schematic indicates it's all connected to the stepped-down side, but I do need to research this more. It is packed into a can of a similar size to the unexploded WWII bomb that's just been floated away from City Airport for a controlled explosion though, and that worries me! Can anyone tell me what's inside and whether I should be reforming it before I go any further? A couple of pics of the transformer are attached.

I have four or five multi-meters, freshly-built lamp-limiter with 15w, 25w, 40w, and 60w conventional bulbs, halogen bulbs 'equivalent to 100w', plus an RCD and 1A and 2A fuses. Unfortunately, no variac though.

I'm itching to fire her up via the lamp limiter, but don't want my enthusiasm to get the better of me, so welcome any advice from forum members who have much more experience than me.

As an aside, I'll have a look over the weekend at the valves and autochanger I pulled out of the scrapped Challenger and post-up some details. I don't think any of them are compatible with the Arkansas, but hopefully they will be serviceable and someone here will be able to make use of them.
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Old 14th Feb 2018, 8:08 am   #19
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Default Re: Blaupunkt Arkansas 43942 Restoration

That big cap/can should be fine, it's probably a Bosch. Take the ECL86's out, leave the radio valves in and power the gram up through the LL whilst monitoring the voltage on the big can. As I said in a previous post it's possible to monitor current if you take the fuse out which is on top of the mains tfmr.

A better way would be to stick another meter in the AC line to monitor current, if current draw goes over 150mA and heads to 200mA switch off.

Clip your meter leads onto the big can etc before you power up so your hands are away from live parts. If you do, do any probing, use your right hand.

Meter or meters in place, the one in the AC mains in set to AC current, the big cap set to DC volts, switch on and keep an eye on things for 10 minutes. DC volts should go up, then down and stay stable, but as the gram hasn't been powered up for a while, volts should steadily climb. AC current should go down. Then leave powered up for a few hours whilst still being not too far away, keep checking V and I occasionally.

If all is steady, take the LL out of the circuit and power up - same meter arrangement, same pack drill. Keep your hand near the switch, any smoke, kill power.

There's a selenium rectifier that may die, near the mains tfmr I think, have a feel now and again (on the body, not the terminals! : ) see if it's getting hot, if so, kill power. Being German made, most of the components are good quality, so you shouldn't need to change much

If all well insert the ECL86's. Good to change C802/807 and C748 and C758 though, as you've done. To check the triode section of the ECL86 red probe on pin 1 black probe to chassis. The triode section is grid biased, (R727/737 will be worth checking) so you should get a negative reading, EG -2v say. If it's positive, switch off. To check the pentode, red probe pin 7, black still on chassis . There should be about 5 volts, positive 5v that is.

Hope that helps, Andy.
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Old 18th Feb 2018, 8:13 am   #20
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Default Re: Blaupunkt Arkansas 43942 Restoration

Andy,

Thanks for your detailed reply. That’s exactly what I needed.

I got the new capacitors in yesterday and have had it fired up through the limiter for a number of hours, starting with a 15w bulb, then 25, then 40w. No problems apparent; the current settled at 97mA and voltages across the two transformer capacitor terminals around 150v and 180v.

I’ve now switched up to a 60w bulb and we’re at 115mA and 187v and 214v. The can and rectifier are cool to the touch, and valves showing a healthy glow.

All looking good at the moment. Hopefully I’ll have time to get it all back together before the day’s out. Will report back this evening.
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