What's this mic' element?

[The Collector]

As per the pic's, this element is fitted inside a non-working Astatic 575-M6 I've just bought from ebay (no surprises there then )

If I recall correctly from taking my battered, free one apart and respraying it in white and gold a few years ago, that one had a circular, silver, perforated element in it at the time.

Is this someone's attempt at replacing a faulty element or did later beige-boarded ones have this rectangular thing in instead????

Also, some of the soldering is terrible and I could manage better whilst soldering left-handed, whilst drunk and whilst walking a tight-rope.

I only bought this to have a play with and it's a good job too Luckily it was pretty cheap at £35 posted.

Thoughts...???

[The Collector]

A few more:

[14CS06]

Hello

I hope it can help you



@+
Claude

[14CS06]

Hello

More

@+
Claude

[14CS06]

Hello

@+
Claude

[ch25]

http://www.sinequanon.co.uk/moving-coil ... dance.html
Could be KNOWLES 2390 too.
Same mic element Bob Heil put his stickers on and sell for big $$$.
Chris

[The Collector]

Merci Claude - nice pictures as usual and they help with sorting out some of the soldering queries.

Chris - thanks for that info. I've never seen that type of element before, although that's not surprising as the limit of my microphone expertise is removing the foam to make the mic' sound a bit louder and less muffled!

If that element is good enough for Bob, then who am I to argue?

I just need to do a bit of tidying solder-wise and suss out why there's no audio. Maybe the resoldering will just fix it (I live in hope)?

[The Collector]

Well I've resoldered the mic' plug end, chopping off the naffly-soldered stuff and redoing it for Cybernet rather than Uniden as it was. I've touched up some of the dodgy-looking solder points just in case there was a dry joint, all to no avail thus far...still no audio.

A couple of thicko questions from someone who knows bugger-all about mic's (and most things electronic):


* Should the mic' element itself have continuity between + and - ?

* Should the blue, screen AND black wires that go down the mic' cable ALL have continuity at the board (I know the blue and screen should as they're soldered together at the plug end)?

* What's likely to cause a lack of audio component-wise if it's not the element?

Cheers all

[Mitch]

It could be the element or component failure. Tbh I thought the Astatic mics had a ceramic/crystal element (like the K40's and old TW232's), which have a very high impedence, reads very little continuity and clicks when tested. If the element you have has low impedence (little resistance, like the one in the link Chris posted) then you could have a dynamic (moving coil) mic that is incompatable with the circuit design, possibly, I'd have to see and measure them myself so I'm only guessing at the moment. You could try connecting the mic element directly to the mic input on the radio (like a normal mic), missing out the circuit, to see if there's any sound, CB's are usually made for 600 ohm dynamic mics so you might get something even if only to test it, otherwise an audio signal generator would be useful to diagnose the board.

From the diagram Claude posted (merci) the black wire is the RX ground (speaker to earth on receive, not to earth on transmit), it looks as if the blue wire is the only one connected to screen, other options are for the likes of old 60's type CB's with seperate circuits. It doesn't look too hard to suss out imho, just time and patience mostly.

[The Collector]

I didn't think to key the mic' to see if the black disengaged, so I can try that tomorrow.

I have an old, manky Altai echo mic' that's only fit for the bin, so I could take that apart and see if the element works in the Astatic at all.

Otherwise, I can remove the weird, rectangular element from the Astatic and pop it in a dynamic mic' to see if anything comes out of it.

As for the schematic, it looks like a plate of spaghetti to the likes of me!

Cheers Mr. Mitch

[wa10]

looks like a heil hc4/5 ceramic cartridge, where are the terminals, on the back or on the end ?

original cartridge is silver with black front, later bob & bart boards had all siver cartridges & to my ears sound a little more metalic or less warm,
at least you got the good version of 575 with a propper switch .

[The Collector]

The solder terminals are on the back plate, right at the bottom edge.

I have a multimeter but don't know how to use it properly to be honest, other than for DC volts and continuity and all I know, is that the cartridge shows continuity

If I get chance to have a look at it later, I'll try the little element I took out of an old Altai echo mic'. It's one of those electret-type things but the look of it. I'm either busy doing DIY in the garden, or helping to home-school our 6yr old until after tea-time

I sprayed the PTT switch with switch cleaner, but that made no difference (was hoping it could've been something as simple as a dirty connection).

[The Collector]

looks like a heil hc4/5 ceramic cartridge, where are the terminals, on the back or on the end ?

Looking at the interweb, it looks like an HC-3 as the 4 and 5 have the solder pads on the very end. Whether it works or not is another matter

I'll see if I can have a go at it tomorrow. Been busy fitting up yards of trellis and chopping down branches of cherry tree and laurel bushes today while we still have decent weather.

[wa10]

If its got continuity its a dynamic cartridge, you can see if its working with a digital multimeter set to AC millivolts,

connect cartridge to meter & whistle into cartridge,
dynamic cb mics usually make about 15-20mv with a good whistle, astatic ceramic 575 cartridge about 50mv.

[The Collector]

If its got continuity its a dynamic cartridge, you can see if its working with a digital multimeter set to AC millivolts,

connect cartridge to meter & whistle into cartridge,
dynamic cb mics usually make about 15-20mv with a good whistle, astatic ceramic 575 cartridge about 50mv.

I'll give that a try too then later... many thanks!