NRG PLL Pro III - will not lock

[BriansBrain]

You see I told you that from the first time but you ignored me.

Sorry you where wrong - It was NOT just adjust VC1

Firstly - I did NOT have the 6.25khz Square Wave on IC1 pin 15
But now I do

[jvok]

Glad you got Brian back on air again.

I take it you put the original xtal back in? That impedance plot is about what I'd expect for a working xtal: https://i.stack.imgur.com/iPwm2.gif

Sounds like it was one of the caps that was bad, or maybe tiny invisible solder crack that you fixed when you changed the cap.

[BriansBrain]

Glad you got Brian back on air again.

Thanks
I have a stand byTugicom TX180 1W exciter so that kept me ''ON AIR''

I take it you put the original xtal back in? That impedance plot is about what I'd expect for a working xtal:

Yes I put the original Crystal back in, especially after I did the test with the Spectral Analyzer and...
after I did a Search and found out that that's what a Crystal plot was supposed to look like

Sounds like it was one of the caps that was bad, or maybe tiny invisible solder crack that you fixed when you changed the cap.

I could not put my finger on what exactly but all is working fine now

What baffled me was it had already been working flawlessly for over a year before it went into No Lock Fault mode

.

[LeeCavanagh]

I cant get a lock, (even tho the green light is on all the tine) and non of the switches to change the freq make any difference.,
- should that chip and switches still at least make a difference yo the freq output even when not exact lock is made ?

I changed the crystal but no difference (i should probably find the old one and create a test circuit for ir?)
I must be missing the obvious but its getting me down now, seriously.
I dont have a scope, only freq counter, multimeter

I have 2 boards, 1 works flawlessly and 1 doesn't,
Using same 13.8v power supply which is a good one.

I dont get any static freq display on my frequency counter from pin 15 it just keeps changing (i did wonder if its not helped by a nearby radio tower), i can get a static freq from the main output transistors tho enough to tell the counter works,

Overall the freq on my tuner just jeep creeping up slowly whilst it warms up, like the vco old days

should i try anything else ? I

[LeeCavanagh]

I think my issue is still voltage related.
The 13.8v is being pulled down to13.6, and the 5v is showing as 4.8v would that be enough for the chips to non-function sufficiently? I get a solid 13.8v when i disconnect the nrg board.

[LeeCavanagh]

Ic1 pin 16 I get 7.42v, still nothing steady on pin 15.

My power rails are not spot on, and the R37 that I replaced (because the old one was scorched) has also now scorched and it not been running on the dummy load long,

I’m tempted to use my mean well 5v supply to the NRG 5v rail and see if everything else fires up…

Perhaps someone could tell me what could cause R37 to run so hot it scorches the outer shell (and I’ve popped in the new one I mention, which is far higher watts than it needs so something has got to be causing it? Ic5 , or a cap maybe, would you just recommend changing all the caps in the voltage regulator section?

And what kind of voltage tolerance is acceptable on the 2 rails?

Thanks very much

[Krakatoa]

Ic1 pin 16 I get 7.42v, still nothing steady on pin 15.

My power rails are not spot on, and the R37 that I replaced (because the old one was scorched) has also now scorched and it not been running on the dummy load long,

I’m tempted to use my mean well 5v supply to the NRG 5v rail and see if everything else fires up…

Perhaps someone could tell me what could cause R37 to run so hot it scorches the outer shell (and I’ve popped in the new one I mention, which is far higher watts than it needs so something has got to be causing it? Ic5 , or a cap maybe, would you just recommend changing all the caps in the voltage regulator section?

And what kind of voltage tolerance is acceptable on the 2 rails?

Thanks very much

R37 slowly cooking means you have too much current draw from the PLL section.
You may start by suspecting the voltage regulator maybe it is damaged and overconsuming.
Then check the logic chips. If you have in there any old TTL family (not HC or LS) they consume quite a lot, replace them by newer ones.
Other possibility is a decoupling capacitor going leaky and pulling current (cheap chinese ceramic caps can do this over time).

[LeeCavanagh]

Ic1 pin 16 I get 7.42v, still nothing steady on pin 15.

My power rails are not spot on, and the R37 that I replaced (because the old one was scorched) has also now scorched and it not been running on the dummy load long,

I’m tempted to use my mean well 5v supply to the NRG 5v rail and see if everything else fires up…

Perhaps someone could tell me what could cause R37 to run so hot it scorches the outer shell (and I’ve popped in the new one I mention, which is far higher watts than it needs so something has got to be causing it? Ic5 , or a cap maybe, would you just recommend changing all the caps in the voltage regulator section?

And what kind of voltage tolerance is acceptable on the 2 rails?

Thanks very much

R37 slowly cooking means you have too much current draw from the PLL section.
You may start by suspecting the voltage regulator maybe it is damaged and overconsuming.
Then check the logic chips. If you have in there any old TTL family (not HC or LS) they consume quite a lot, replace them by newer ones.
Other possibility is a decoupling capacitor going leaky and pulling current (cheap chinese ceramic caps can do this over time).

Thanks for your quick reply, appreciated, yes I agree changing regulator and caps, will post update when those components have been received / replaced.
Maybe I should replace some of the ceramic disc caps for tantalum
I

[Albert H]

DO NOT fit tantalum capacitors. They're notorious for random failures, are relatively expensive and easily wrecked by putting them in the wrong way 'raound, or by overheating during soldering.

They're nasty things!

[LeeCavanagh]

DO NOT fit tantalum capacitors. They're notorious for random failures, are relatively expensive and easily wrecked by putting them in the wrong way 'raound, or by overheating during soldering.

They're nasty things!

Think I was mistaking them for Silver Micas ? They are good for rf but more expensive that’s the oneisnt it?
And the others I know need to be electrostatic where specified on the drawing.

Any way, if put orders in, not for everything but I’ve spent 45quid, hopefully some 1! Tollerence ones, and the rest are 5 or 20 for the electrostatics as I. Couldn’t warrant the audiophile caps prices. You said buy pack in the past which I did from stone places but don’t know how good or bad they are, just hoping that the nag board was designed with relatively generic tolerances requirnents, but I wanted 1% fir the caps around the poll and voltage regulator

[Albert H]

There is no point whatsoever in using 1% electrolytic filter capacitors on those supply rails. The ones supplied with the original kits were 10% at best!

"Audiophile" capacitors are purely for Audiophools - they're a complete rip-off. I've designed and prototyped a lot of commercial broadcast equipment, and a few years ago - when the exotic "Audiophile" Electrolytic Capacitors became available - we ran a whole lot of tests on them, to see if they were worth the huge difference in price. They're no better than ordinary branded electrolytics - they're very slightly better than the cheap generic Chinese ones (lower leakage, less microphonic), but you really won't hear any difference.

A quick tale from my past:

My friends and I used to know a guy who worked for a very high-end audio equipment store in the West End of London. This store used to boast about its "acoustically perfect" listening rooms, where prospective buyers could compare the relative merits of the extremely expensive equipment they used to sell. One night in the pub, he was boasting about this "amazing" speaker cable that they were selling for £22/yard (this was the late 70s!) and that it was the "best he'd ever heard".

A few days later, on another visit to the pub, we persuaded this guy - let's call him "Trevor" - that we'd discovered our own superb speaker cable that cost rather less, and that we'd be happy to bring some to the shop, and he could try it out in comparison to his "amazing" cable. We arranged to meet on the next Saturday afternoon, and suggested that he selected his favourite turntable, cartridge, preamp, power amp and speakers, and assemble the system in one of the listening rooms - we'd connect one pair of speakers with his cable and another identcal pair with our cable, through a switchbox (the speaker switchbox cost £300, so it must have been good). The system would have cost well over £22000!

The testing afternoon arrived, and we went behind the "acoustically transparent" curtaining to wire up one pair of speakers with our cable.

We ran "blind" tests, using all his favourite albums, and invited several of the other staff and customers to also audition these cables. Nobody was able to tell them apart. They were "acoustically identical" according to Trevor and his boss.

He actually burst into tears when we revealed that our "speaker cable" was actually white 2-core 5 Amp lighting flex from Woolworths just along the street (18p/metre in those days!). He blustered, claiming that the amplifier "would handle any load", and we pointed out that if there was any difference in load presented to the amplifier, it didn't matter at all what you used to connect the amplifier to the speakers! Poor Trevor got even more upset when we pointed out that if any cable actually made a difference to the sound coming from the speakers, the cable must be faulty!

It just goes to prove that there's no Fool like an Audiophool!

[mikroman]

human brain games

[LeeCavanagh]

Albert I got them for the tolerance not for audio qualities, clearly the ones in there were not good enough or the wouldn’t have gone faulty, but thanks for waiting till after I’d purchased them to give me a kick in the nuts ( wink )

[Shedbuilt]

@LeeCavanagh Just a thought, your frequency counter will most likely work to pick up the logic signals (for example 6.25KHz from pin 15 of IC1. That connects to pin 12 and 10 of IC3. Pins 13 and 9 of IC3 are the other inputs of those Exclusive Or gates, and receive the signal from the output frequency (or 1/2F) divider chain. When in lock, the frequencies on pin 12/10 and pin13/9 should be the same. Checking there would be a good first step. Those two gates provide output to the loop filter (PLL control), and lock detection / OLPD.

[LeeCavanagh]

@LeeCavanagh Just a thought, your frequency counter will most likely work to pick up the logic signals (for example 6.25KHz from pin 15 of IC1. That connects to pin 12 and 10 of IC3. Pins 13 and 9 of IC3 are the other inputs of those Exclusive Or gates, and receive the signal from the output frequency (or 1/2F) divider chain. When in lock, the frequencies on pin 12/10 and pin13/9 should be the same. Checking there would be a good first step. Those two gates provide output to the loop filter (PLL control), and lock detection / OLPD.

All those pins are giving me total random frequencies constantly changing.

[Albert H]

Your crystal is probably knackered or IC1 is fried. The signal out of pin 15 of IC1 should be a nice chunky 5V squarewave at 6.25 kHz - any frequency counter should be able to show that.

[LeeCavanagh]

Your crystal is probably knackered or IC1 is fried. The signal out of pin 15 of IC1 should be a nice chunky 5V squarewave at 6.25 kHz - any frequency counter should be able to show that.

But I replaced the crystal and ic1 already,
I have not yet received my new regulator and caps but if you think that I need yet another crystal and ic1 I will replace after I’ve done the other bits (to prevent any further damage).
i don’t get 5v on in 15, I need to check again but recall I was getting 3.65v and pin 16 was 7.4v. If that means anything to you

Thanks Al
Regards Lee

[LeeCavanagh]

On the board that works I get 7.6v on pin 16
Ic1 And I get 3.73v on pin 15 ic1 of the board that works

On the board that isn’t working properly i’m still seeing too much heat on resistor R37 (hence why I think wise to wait till I’ve changed some of the regulator components before I go trying again probably get to do that on Wednesday.

I did also try my frequency counter on the board that works but surprisingly I don’t get a static reading on that either for ic1 pin 15 (but i do get a perfect reading out of the pa stages, so it looks like my frequency counter can’t do the low mhz , it was only £7 tho )
I will do what you suggested and get myself a scope,

[Krakatoa]

You will not get 5V in pin 15 because the multimeter averages the voltage of the square wave, unless the output is stuck at logic level 1.
It all sounds like you have a quite unstable power rail. Try bypassing the 33 ohm resistor before the voltage regulator and see what gets hot. If you are afraid of frying everything, put instead of the resistor a 200mA fuse...

[Shedbuilt]

IC1 supply (pin 16) should be around 7.5V. This is a CMOS 4060B. It’s supplied from it’s own 7.5V Zener Diode. The 74 series chips are supplied from the 5V rail (as is the HC4059).
When you tried to use your frequency counter on the logic signals, did you connect the counter ground to the PCB ground ?