Hacker RP 25 -Motorboating now now AM and high quiescent current

[ppppenguin]

The AF114 which I used as a replacement for T3 I tested with a multimeter (with specific PNP and NPN holes -if you know what I mean), and as it had a high hFE value (around 500) I assumed that the whisker problem didn't exist.

I can't imagine an AF11x transistor having an hFE anywhere near 500. This would be high even for a modern device. Either the device is faulty and misleading the meter or something is wrong with the meter.

[Bonky]

argh!
I'm obviously out of my depth here.

Time to give it to the pros I think!

Many thanks,

Richard

PS ( I have 3 more AF114s - all have similar hFE readings. Another was dud as it showed no reading at all).

[Bonky]

Having said all that, is this too cheap to be true:

http://www.ebay.co.uk/itm/TSG-17-High-Fr...Ciid%253A1

Richard

[Terry]

That hFE reading is definitely wrong!

As far as your current signal source  is concerned, I'd suggest the 'quick'n'dirty' approach. Swing the generator frequency back and forth across the frequency of interest. If the receiver works, you will hear a sort of 'squmpf' as you tune through the IF band, just like tuning through an unmodulated broadcast signal.

This also serves another purpose: if your generator calibration is out or the set has been incorrectly aligned at some point, this method will still work even though the set actually works at an IF frequency other than 470hHz or your generator frequency is wrong.

[Bonky]

That hFE reading is definitely wrong!

As far as your current signal source  is concerned, I'd suggest the 'quick'n'dirty' approach. Swing the generator frequency back and forth across the frequency of interest. If the receiver works, you will hear a sort of 'squmpf' as you tune through the IF band, just like tuning through an unmodulated broadcast signal.

This also serves another purpose: if your generator calibration is out or the set has been incorrectly aligned at some point, this method will still work even though the set actually works at an IF frequency other than 470hHz or your generator frequency is wrong.

Hi; thanks.

Do I gather that I use the 'sweep' function on the SG - with the 'baseline' of 470kHz? If so, to what extremes? (e.g. +/- 100kHz).

BW

Richard

PS I'm always up for the 'quick and dirty' approach - with precautions of course.

[Refugee]

That sig gen linked a few posts back does not do FM making it less useful if you want to do an FM set later.
The sweep function on your present sig gen should produce something on the audio output of the radio.

[Bonky]

That sig gen linked a few posts back does not do FM making it less useful if you want to do an FM set later.
The sweep function on your present sig gen should produce something on the audio output of the radio.

Thanks.
Richard

[Murphyv310]

Hi.
Personally I'd not recommend either the signal generator you have nor the one you are looking at for a beginner, they are too complex to drive and neither has an internal audio test tone modulated onto the RF output.
I'd be looking for an older simpler one like an Advance, simple controls and accurate enough for a tranny radio and cheaper too. To be fair you've already paid out a good few quid and if you think this is going over your head stop and perhaps work on something easier or make a few little projects to get familiar with electronics.
If you wish to carry on I'm sure we will help as much as possible.

[pwdrive]

The sig gen in the last link would do, you don't need an FM generator or sweep facilities at this stage in your radio career, there's possibly at least one niggle I can see, It looks as though the output attenuator might be and adjustable preset if so then that might be a bit of a pain.

My recommendation would be an old style second hand job that's known to be working, the ones I have owned and used over the years both in and out of trade were the Advance E2, an excellent generator for servicing radios, does not cover the full VHF/FM band but to be honest that facility would rarely be needed as most FM tweeks at VHF can be done using on air transmissions.

The others I've owned/used were mainly Avo's, those being the Avo All Wave, the Avo Wide Range (aka the MK1) and the Avo CT378a, all excellent generators but bear in mind that the CT378a, excellent though it is, only goes down to 2Mhz.

Also had a Marconi TF144G, bit of a lump but a very good generator but the weak point is the thermocouple for the output meter, more often than not it's shot and not obtainable, the one in mine was ok.

All the above except the Avo CT378a will do all the common IF frequencies including FM IF frequencies, all the above have built in internal modulation facilities and both stepped and variable attenuators.

The most popular trade sig gen back in my day was the Advance E2.

EDIT: Post crossed.

Lawrence.

[Murphyv310]

Hi.
Lawrence is echoing my advice.
The way I see this is the radio is a 60's design and the vast majority of service departments would have had an Advance or possibly an Avo signal generator and be using it for exactly the same problems you are encountering. Modern ones are overly complex and often don't have the basic minimum features you need.