Motorola Console Salvage

croat47 · 15th February 2009, 02:28 AM

I've posted about the speakers in another thread: http://www.diyaudio.com/forums/showt...43#post1745443

But, I've got some questions about the tube amp in an old Motorola console stereo. The tuner/phono stage is loaded with 12AX7. The power seems to come from a pair of EL84 per channel. Will have to re-check the stage before that. But:

1) What are the little white nodules on the outside of some of the tubes?
2) There seems to be a large amount of wax coming out of the chassis hole from the transformer...is the transformer blown?
3) Many of the signal chain caps are Motorola and have wax on the ends. Nothing looks to dry. Worth trying to re-use?

I will try to post picks of the wax buildup that seems to be from the transformer.

The model is a SK18-M. Anyone know anything about these? Thanks!

DigitalJunkie · 15th February 2009, 02:47 AM

The wax leakage was sort of normal.It kinda tends to 'creep' out over the years.
If it looks like the wax has all been melted,and poured out of the transformer,that might be a sign of an overheated transformer. To be sure,check it for continuity with your DMM.

The old waxy caps are probably not worth re-using.Those older types of caps tend to be electrically leaky,some new 'Orange Drops' will only run a couple bucks so it's worth replacing them.

The white nodules on the tubes-I'm not entirely sure what you mean?

Sounds like it might make a nice little amp project. Good luck,let us know how it goes!

croat47 · 15th February 2009, 12:03 PM

It does not look as though it has poured out. The leads have some clumps on them. I will post a picture...

The nodules are small, white grains on the outside of the tubes. Looks like someone powdered a few with confectioner's sugar.

Tom Bavis · 15th February 2009, 02:18 PM

Sams folder 445-8 (1959) covers the SK-18M. I might have a copy - I'll look.

The wax caps are bad - replace them. The transformer is probably fine - they can run considerable above the melting temperature of wax.

15th February 2009, 02:28 AM	#1
croat47 diyAudio Member Join Date: May 2005 Location: Eastern Shore, Maryland	Motorola Console Salvage I've posted about the speakers in another thread: http://www.diyaudio.com/forums/showt...43#post1745443 But, I've got some questions about the tube amp in an old Motorola console stereo. The tuner/phono stage is loaded with 12AX7. The power seems to come from a pair of EL84 per channel. Will have to re-check the stage before that. But: 1) What are the little white nodules on the outside of some of the tubes? 2) There seems to be a large amount of wax coming out of the chassis hole from the transformer...is the transformer blown? 3) Many of the signal chain caps are Motorola and have wax on the ends. Nothing looks to dry. Worth trying to re-use? I will try to post picks of the wax buildup that seems to be from the transformer. The model is a SK18-M. Anyone know anything about these? Thanks! __________________ Regards, Aaron

15th February 2009, 12:03 PM	#3
croat47 diyAudio Member Join Date: May 2005 Location: Eastern Shore, Maryland	It does not look as though it has poured out. The leads have some clumps on them. I will post a picture... The nodules are small, white grains on the outside of the tubes. Looks like someone powdered a few with confectioner's sugar. __________________ Regards, Aaron

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15th February 2009, 02:47 AM	#2
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	The wax leakage was sort of normal.It kinda tends to 'creep' out over the years. If it looks like the wax has all been melted,and poured out of the transformer,that might be a sign of an overheated transformer. To be sure,check it for continuity with your DMM. The old waxy caps are probably not worth re-using.Those older types of caps tend to be electrically leaky,some new 'Orange Drops' will only run a couple bucks so it's worth replacing them. The white nodules on the tubes-I'm not entirely sure what you mean? Sounds like it might make a nice little amp project. Good luck,let us know how it goes!

15th February 2009, 02:18 PM	#4
Tom Bavis diyAudio Member Join Date: Jun 2002 Location: Macedon NY	Sams folder 445-8 (1959) covers the SK-18M. I might have a copy - I'll look. The wax caps are bad - replace them. The transformer is probably fine - they can run considerable above the melting temperature of wax.

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