Hacker GP 42

[unitaudio]

Over the weekend I became the very happy owner of a slighly down-at-heel Hacker GP 42. I duly downloaded the service information and schematics from this website and had a butcher's...

Smoothing can and grid coupling caps will be replaced as standard procedure. I powered it up for about 5 seconds and it buzzed even though the valves hadn't warmed up so it seemed safe to assume the above are past their best.

One thing slightly concerns me, the ventilation grille on the underside beneath the valves has got a bit melty at some point. Looking inside and removing the amplifier chassis, it doesn't seem that the transformer has had a particularly hard time at any point but I can't help thinking the valves alone really shouldn't get hot enough to melt the grille. Given the price of a matched pair of ECL 86's, it is the cause of much trepidation...

I know I shouldn't necessarily let it worry me yet, I need to replace the caps and test voltages with the valves out before jumping to conclusions but is it me or does the melted grille suggest anything ominous?

Regards,
Paul

[jjl]

The hum from the 'speaker before the valves have warmed up is likely to be due to magnetic coupling between the mains transformer and 'speaker transformer and is not an indication of component failure; it's quite normal with some sets.

It would be wise to replace each coupling capacitor to the ECL86 pentode grids, but I'd suggest only replacing the smoothing can if absolutely necessary.

The "molten" grille may just be due to the grille distorting over time; elderly plastics are quite capable of this sort of behaviour.

John

[unitaudio]

The hum has mains buzz superiposed over it and it's loud enough not to be normal. It would be well audible over the music. I realise a certain amount of hum is inevitable from experience with other valve players in the past but this is excessive. It sounds like a floating input but it can't be that because it wasn't on for long enough for the valves to warm up.

Speaking of floating inputs, I have yet to ascertain whether the cartridge is any good or not. All things in due course...

Yes, some old (and not so old) plastics can behave strangely, especially if left in contact with something they take exception to! I suppose it could've been left to sit on something it didn't find agreeable. All the other plastic mouldings present are in good condition so that could indeed be the case.

Regards,
Paul

[Edward Huggins]

I think you may be hurridly jumping to conclusions as to what may or may not be wrong with the GP42. I can assume you, given its circuit design, there should be a very low level of hum on this - it's a Hacker after all. If your version has the Garrard 2025TC autochanger, then the cartridge will be an Acos GP96-1. Also, let me assure you that a deformed grille is a very common sight on many of these Hackers and is not just confined to yours.

[kirstyd]

The grille tends to melt when the air flow is restricted usually caused by prolonged use on thick carpet. I know because I did it with my brand new GP 42 back in 1969.

[Lucien Nunes]

it wasn't on for long enough for the valves to warm up.

Then logically the hum can't be due to a failed smoothing can because there won't be any HT on it or flowing through the output transformer. So you have no indication yet whether it is good or not and I wouldn't make any assumptions, other than it would be wise to replace the coupling caps unless a trustworthy type is already fitted.

I prefer to reform and test before powering on; not all cans are OK but the last few I have done have been electrically as good as new. The process doesn't need to be complex especially with a transformer-fed set. Slipping 47k in the rectifier cathode or CT ground lead and leaving the set on for 30 mins with only the rectifier in, can bring it back to good health. Yes the voltage will be high, not usually damagingly so unless there are lower-rated caps further down the chain and there aren't in the Hacker.

[nigelr2000]

I had a GP42 come in with a hairy grill, it had been used on a thick pink coloured carpet, I knew the colour as it was all stuck to the grill, bet they were annoyed to have a Hacker shaped bit of carpet ripped off

[unitaudio]

Thank you for all the replies.

Edward, yes it's a 2025TC with a GP96-1 but it needs so much work that I'm going to replace it with an SP25 mk2 I already have. I only ever use autochangers in manual mode anyway so losing it is no big deal.

Kirsty D, ah that makes sense. I'm not really bothered about the grille itself, it's underneath so it can't usually be seen and cosmetically this player has bigger things to worry about! As long as it's not a portent of anything more sinister, I'm happy.

Lucien, of course, the can is after the rectifier! I suprise even myself sometimes...

This record player is never going to win any beauty pageants as it's not even close to mint but I just want it to work as intended and be reliable. I've wanted one for such a long time and I guess I got a bit worried because certain bits can be expensive.

Regards,
Paul

[Edward Huggins]

If you are going to retire the Garrard autochanger, you certainly can re-use that Acos GP96-1. It is well suited to your SP25 - they are an excellent cartridge.

[Michael Maurice]

The coupling caps on a GP42 are the Mullard mustard types and normally do not require replacing.

[unitaudio]

Edward, I found that the rubber that the stylus shank sits against is missing! That came as a bit of a blow because I've always regarded Sonotone cartridges to be about the best ceramics you can get. I'm going to have to consider my options. I want to avoid the red/black Chinese option if I can.

Michael, thanks for confirming that for me. I thought they might be mustards but I only gave the amp chassis a cursory glance and I was going to have to have another look.

At the moment it's looking like some switch cleaner in the pots and a solution to the cartridge debacle will see this one working again! I'm doing the record deck transplant this afternoon.

Regards,
Paul

[Edward Huggins]

I am now confused. I thught we were talking about an Acos GP96/1 cartridge, now you mention a Sonotione? Please clarify your intentions as I thought you were gonig to use a SP25 and then fit the (assumed working) Acos.

[unitaudio]

Sorry Edward, you're right, Acos, not Sonotone. My mistake.

Regards,
Paul

[unitaudio]

I fitted the SP25 deck and ordered a BSR SC12M cartridge which arrived 3 days later. I fitted it and gave it a try. It worked and the Hacker gave me a taste of what it's capable of. However, the experience was spoiled by very high hum and noise.

I knew at the very least the control pots needed the Servisol treatment so I removed the record deck and peered inside again.

I noticed the floor of the cabinet was covered by a sheet of self-adhesive foil. The control panel and the socket panel at the back were RF shielded by it but all the foil was badly oxidised and was in the process of becoming a powder and had many gaps where it had rotted away completely.

I had some rolls of 2" wide aluminium tape and so began the long-winded job of scraping away the old foil. It took most of Saturday and I replaced the foil with the aluminium tape on Sunday. Then I did what I originally intended to do and gave the pots a good spraying and worked them back and forth for a while.

Massive improvement! Hum and noise was extremely low even at high volume. It sounded incredible for a portable record player that's about the same age as I am! Job done - or was it?

After one side of an album I noticed the mains buzz had crept up again. By then it could be heard above the music. It definitely wasn't like that when I first switched on.

Reading over old posts on this forum, I saw that Michael Maurice always replaces R6 & R7 when servicing these players. I haven't replaced anything yet so these are on the list for starters but what rating are they? In the service info they are 220k ohm but no power rating is given. They're big chunky old things so I'm guessing at least half a watt.

Coupling caps are Mullard Mustards so I'm not concerned about them but what about the main smoothing can? I need to run it for a bit again with the record deck removed to ascertain whether or not the can is getting hot.

Given that this record player was in a pretty sorry state when I got it, I'm very pleased with progress so far and it's getting close to working as intended.

Regards,
Paul

[Vintage Engr]

Unitaudio, if you can post a picture of the grille, I think I may have a spare one. I repaired one of these a while back, & changed both grilles for a similar, but not identical type. I thus have one good original.

David.

[unitaudio]

David, that's brilliant because mine has a dent which has proved very difficult to straighten out. I'll be able to post a picture tomorrow. Thank you very much!

Regards,
Paul

[unitaudio]

Photos of Hacker Gondolier as reqested.

[Vintage Engr]

Ah, sorry Paul -

Wrong grille, I'd not realised it was the front Speaker grille with the problem.
Sorry about that, on the version I repaired there was a plastic vent grille on the underside of the cabinet, which melted, as the unit had been stood on carpet & overheated. It's that grille that I have a good spare of.

David.

[unitaudio]

The one on mine is melted too so I'd still be interested. I thought you meant the front one.

Regards,
Paul

[Edward Huggins]

Nearly all these metal perforated grilles get dented over time. When you remove the 10" x 6" speaker, you might just be able to ease out the dent which is sited just over the right hand side of the 9.5" wide cone baffle cut out.