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Chris55000 · 20th Mar 2019, 12:39 am

Hi!

What tends to happen is that the much heaver battery current of the TV section compared to the radio and tape sections tend to burn out the contact wiper as well as the fixed contact, resulting in the radio and tape sections working intermittently or not at all because of the excessive drop across the burnt contacts.

There will normally be three switched 10–11V stabilised rails in this type of combination unit – one lead will lead off to the TV board, a second will feed the tape preamplifier panel (sometimes via a further switch on the cassette mechanism itself so the amp comes on in 'play' mode), and a third lead to the am/fm if circuits of the radio section.

The audio output stage will be directly fed from either the battery/mains unit direct (it doesn't need voltage stabilisation), or from a direct ouput of the 11V stabiliser.

It's worth having a look at the AM/FM/TV function selector switch carefully – (unfortunately I've not had one of these combos for years I'm afraid, and I couldn't find the circuit–diagram for your set, so I can't be more specific!) as there may be an unused section where you can transfer the battery switched wiring to, or, if the switch is directly soldered to the pcb, you might find a spare row of tags containing a complete free section or "pole" you can reuse with a few carefully run link wires!

If the switch has no spare contacts you'll just have to do the best you can with switch–cleaner!

Chris Williams

20th Mar 2019, 12:39 am	#7
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,870	Re: Waltham W154 issues Hi! What tends to happen is that the much heaver battery current of the TV section compared to the radio and tape sections tend to burn out the contact wiper as well as the fixed contact, resulting in the radio and tape sections working intermittently or not at all because of the excessive drop across the burnt contacts. There will normally be three switched 10–11V stabilised rails in this type of combination unit – one lead will lead off to the TV board, a second will feed the tape preamplifier panel (sometimes via a further switch on the cassette mechanism itself so the amp comes on in 'play' mode), and a third lead to the am/fm if circuits of the radio section. The audio output stage will be directly fed from either the battery/mains unit direct (it doesn't need voltage stabilisation), or from a direct ouput of the 11V stabiliser. It's worth having a look at the AM/FM/TV function selector switch carefully – (unfortunately I've not had one of these combos for years I'm afraid, and I couldn't find the circuit–diagram for your set, so I can't be more specific!) as there may be an unused section where you can transfer the battery switched wiring to, or, if the switch is directly soldered to the pcb, you might find a spare row of tags containing a complete free section or "pole" you can reuse with a few carefully run link wires! If the switch has no spare contacts you'll just have to do the best you can with switch–cleaner! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!