Wireless Mikes ?

GR = frequency sub-group

internal

and

Looks a right mess under a 30x. They must have screwdrivered it hundreds of times before neatly prizing off a SMD SOT23, leaving 3 non-virgin pads. First guess topmark LG like most of them around , NPN yes, my list says UHF BF775 - unlikely . Will try anything GP that is NPN , pin1 68K to it is assumed base, p2 gnd E, p3 1k so C assumed. For completeness LG = ? Other SO23 are SOT23 FET probably , marked XY NPN SOT23 marked FV then sideways 18 small script, probable pinning p1 E, p2 C, p3 B if anyone has topmarks for about 2005

Label on the mike is worn , no wonder I could not find pics, it is an FM 64. No bit of wire dangling so the zigzag is the antenna. So what is the bit of multistrand thick wire, about 4mm long, inside a black housing that looks like a 2.1mm DC power connector, if it was a solid conductor at the centre?

Anyone know if you can use the top end of an analogue UHF TV to check these

850MHz mikes, as far as some sort of modulated signal or at least active carrier? The mating receiver is in a fixed installation

2. > No bit of wire dangling so the zigzag is the antenna. So what is the bit

of

centre?

It would seem to be a mangled DC power connector for rechargeable batteries option and one of the traces from it is zigzagged and UHF overlain on it for radiating out.

Gemini FM 64 radio mike Soldered in a GP SOT23, BCW31 topcode D1. On 3V the LED flashes on switch on, goes goes continuous if V drops to 1.4V and current goes well over 100mA before that. With 3V, current draw is 69mA and 68mA without the electret mike plugged in but no change in draw with tapping of mike. Nothing on the LM317 so I will assume that is for DC feed for rechargeables, not used for the main circuitry.

Dug out an ancient early portable colour TV, retained for just such a purpose. So old it has a VHF rotary tuner built in as well as UHF. But of course nice old mechanical rotation for VT to tuner block, so can play around as much as you like detuning either side to try and get some sort of audio demodulated. At the top of the range around ch 68 a strong signal including interference pattern on picture,from the other end of the room, all going on switching off the radio mike. No amount of fiddling of de-tune would get even a semblance of sound on tapping the mike nor change of interference pattern on screen. At this stage without proper test equipment I will assume working entirely until the owner tells me otherwise. Still don't know what the third position of the slide switch is. Maybe only

2 positions used of the 3, going by the length of slot in the outer bezel, but the plastic widget that extends up from the pcb slide sw is missing, hence plenty of space to scrape a screwdriver around inside. The surround Al of the slide sw was so randomly scraped I thought it was brush finished when I first saw it, hence probably hundreds of screwdriver activations. Now to bodge up a widget

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Made a widget from a bit of VHS tape cassette outer, kids plastic mosaic bead, cutdown plastic snap rivet, hotmelt glue and some silicone paste so it slides easily and looks almost proper-like , original never seen.

UHF TV test does work to the extent you can de-tune to a point where tapping on the mike will modulate the interference pattern on the screen and at another point a feint tapping in the audio.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Back in service Sw is off/carrier on/carrier plus modulation

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Think you've got the record for a one man thread. But interesting. ;-)

--

*Middle age is when work is a lot less fun - and fun a lot more work.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW To e-mail, change noise into sound.

It`s the digital equivalent of talking to yourself ;)

Not when its collated together, corrections made and placed for all, gratis, with hundreds of other such repair briefs , already uploaded at the weekend on

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Most likely originally labeled "off/mute/on," and this (or something roughly equivalent) is standard for most wireless microphones. Switching the transmitter completely on and off will often cause pops and other objectionable output, so for temporarily suspending use the mute setting is useful. Of course, ideally a competent sound tech will take care of muting and so forth at the sound board, but that's not always reality.

--
Andrew Erickson

"He is no fool who gives what he cannot keep to gain that which he cannot
lose."  -- Jim Elliot

AKA: Cough Switch.

--
Greed is the root of all eBay.

Now , from being back in use, in the mid position the led on the receiver, for that ch, goes on, then sound comes through in third posistion.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Some these days send out a sort of pilot tone which if not present mutes the receiver and prevents it reacting to interference, etc with the transmitter switched off.

--
*Marriage changes passion - suddenly you're in bed with a relative*

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Would that system also work with "taxi breakthrough" of nearby high power Rf generating a whole spectrum of harmonics, not just dealing with mains/triac/wiring rfi noise, flourescent light starter rfi, etc

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I believe that's what it's designed to do. I only use radio mics professionally and would never (intentionally) have a receiver with no input faded up - but I do realise this can happen in churches, etc.

--
*Happiness is seeing your mother-in-law on a milk carton

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Radio mikes with switches are a menace.[1] The 'talent' can't seem to leave them alone, sometimes switching the mike off, then forgetting and glaring at the sound engineer when it`s muted - of course there`s nothing he can do from FoH. The mikes with hidden switches are better, tho often the talent spots the little red light then proceeds to press all the buttons, sometimes going as far as to inadvertently change channels!

Ron

[1] Sorry, make that ALL mikes with switches.

Sadly many churches in the UK need a radio mic for the 'preacher' these days but cannot guarantee having an operator for even a simple mixer. So the user has to be able to mute his mic for singing, etc. But if there's no operator, no one to glare at. ;-)

My brother's kirk is in just this position - and he has asked for my advice about a replacement body pack RM for the minister. The old one was never much good and is getting worse - and it's now illegal in the UK, and has been for some time.

But I only use pro ones - mainly Microns - which are way outside the budget, and I have no direct experience of this end of the market which seems to offer a bewildering choice. My first thought was Trantec as I've used their inexpensive IEM where there is a likelihood of damage.

--
*If we weren't meant to eat animals, why are they made of meat?  

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.