-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
-
Retevis is giving away Radios for the New Year and Every Member is Eligible. Click Here to see the details!
Browning mk lV mic socket
- Thread starter Staybolt
- Start date
The red/white wire was connected to the old socket to power the factory amplified desk mike. Made a battery unnecessary. If the wire is loose, the previous owner wasn't using the stock mike.
Have a look at the relay, and see if the mechanism moves at all when you key the mike. If it moves just a little, the 1000uf filter cap C320 at the very outside corner of the pc board next to the final tube may have gone bad. If it does, there won't be enough voltage to pull the relay in all the way.
If it won't move at all, even a little the PLL is probably out of lock. The channel digits are supposed to go dark when this happens.
But the enormous pile of logic chips in that radio sometimes fails in unpredictable ways.
Or maybe I should say it predictably fails in more ways than you can count easily.
Have a look at the chips on the front-panel boards. The exposed metal "shoulder" of each metal pin is visible where they are each plugged into a socket. If you see what looks like a dark tarnish layer, that chip has silver-plated pins.
Just one of the nightmare issues in the Mark 4 transmitter. That silver oxide gets between the chip pin and the socket contacts. Causes unpredictable parts of the circuit to quit working.
Cleaning them off only prolongs the pain, even when you clean the socket as well. And if that part of the chips' pins look shiny, that chip won't cause that problem. Might cause another, though.
The chips inside the metal shield can run way too hot and are prone to fail. The two 5-Volt regulator chips mounted at the rear of that can will run hot and go bad.
One of them feeds power to the front-panel selector and display boards. The other one powers the chips inside the can. When only one of them breaks down, it puts a sort of "reverse polarity" stress on the one big chip on the front-panel boards. It's a ROM chip famously nicknamed the "poof" chip.
Guess why.
Naturally heat speeds up metal oxidation. If there are any chips with silver-plated pins inside the can, they are almost guaranteed to have a thick fuzzy layer of black silver oxide on the pins.
Bear in mind I'm not trying to get your hopes up here. This is just the tip of the iceberg. Or should I call it a turdburg.
We stopped repairing that synthesizer around 20 years ago. Even after changing out a dozen or two chips, all the electrolytic capacitors, both voltage regulators and the ROM we would see about one out of four units fail in a month or less.
Decided that this is not a "professional quality" result. We stopped supporting that part of the Mark 4. Like whacking yourself on the back of one hand with a hammer. If felt so good to stop.
73
Have a look at the relay, and see if the mechanism moves at all when you key the mike. If it moves just a little, the 1000uf filter cap C320 at the very outside corner of the pc board next to the final tube may have gone bad. If it does, there won't be enough voltage to pull the relay in all the way.
If it won't move at all, even a little the PLL is probably out of lock. The channel digits are supposed to go dark when this happens.
But the enormous pile of logic chips in that radio sometimes fails in unpredictable ways.
Or maybe I should say it predictably fails in more ways than you can count easily.
Have a look at the chips on the front-panel boards. The exposed metal "shoulder" of each metal pin is visible where they are each plugged into a socket. If you see what looks like a dark tarnish layer, that chip has silver-plated pins.
Just one of the nightmare issues in the Mark 4 transmitter. That silver oxide gets between the chip pin and the socket contacts. Causes unpredictable parts of the circuit to quit working.
Cleaning them off only prolongs the pain, even when you clean the socket as well. And if that part of the chips' pins look shiny, that chip won't cause that problem. Might cause another, though.
The chips inside the metal shield can run way too hot and are prone to fail. The two 5-Volt regulator chips mounted at the rear of that can will run hot and go bad.
One of them feeds power to the front-panel selector and display boards. The other one powers the chips inside the can. When only one of them breaks down, it puts a sort of "reverse polarity" stress on the one big chip on the front-panel boards. It's a ROM chip famously nicknamed the "poof" chip.
Guess why.
Naturally heat speeds up metal oxidation. If there are any chips with silver-plated pins inside the can, they are almost guaranteed to have a thick fuzzy layer of black silver oxide on the pins.
Bear in mind I'm not trying to get your hopes up here. This is just the tip of the iceberg. Or should I call it a turdburg.
We stopped repairing that synthesizer around 20 years ago. Even after changing out a dozen or two chips, all the electrolytic capacitors, both voltage regulators and the ROM we would see about one out of four units fail in a month or less.
Decided that this is not a "professional quality" result. We stopped supporting that part of the Mark 4. Like whacking yourself on the back of one hand with a hammer. If felt so good to stop.
73
- No one is chatting at the moment.
