UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Audio (record players, hi-fi etc)

Notices

Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

Closed Thread
 
Thread Tools
Old 30th Apr 2017, 7:37 pm   #101
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: Sony HP-511 - Blowing Fuses

No problem but be aware that the 0.65 volts I mentioned is an approx figure and is not set in stone, a ball park figure if you like.

Lawrence.
ms660 is offline  
Old 1st May 2017, 6:37 am   #102
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,639
Default Re: Sony HP-511 - Blowing Fuses

Your getting somewhere Gareth. To find if a Q is on you measure B and E as Lawrence suggests and I suggested in post # 74 ( no worries it's eay to miss stuff in a long thread). so to clarify that's one meter probe on B the other on E, doesn't really matter which way. As long as you get 0.6v ish the Q is switched on.

I've had a quick look at the manual again and there's a good block diagram on page 3 that shows the signal path. Have a read to see if it helps get your head round the amplifier. When we get the amp running you can check levels by looking at page 2.

I can understand your frustration, it's a bit like stumbling around in the dark looking for a needle in a haystack, hopefully though you'll be rewarded by a high when you fix it. We've all been there and it's tricky to understand what we're telling you and tricky for us to remotely diagnose and fix your amp. Hopefully with a few more heads on board you'll fix it.

I saw this video yesterday that recommends using a program called Every Circuit, it might be worth a look to get a better understanding. See here - https://www.youtube.com/watch?v=VfLgFSroCi8 A bloke called Paul Carlson is doing an electronics coarse on Patreon which is $3 a month, this might help too, see here - https://www.youtube.com/watch?v=Wa86yYSesPM

Lastly here's the schematics of the faulty channel again. Helps folks give advice when they can see what the craic is.

Nil carborudrum illigitimus, Andy.
Attached Thumbnails
Click image for larger version

Name:	Screenshot from 2017-05-01 06-03-04.jpg
Views:	200
Size:	93.5 KB
ID:	141909   Click image for larger version

Name:	Screenshot from 2017-05-01 06-03-40.jpg
Views:	214
Size:	96.5 KB
ID:	141910  
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline  
Old 1st May 2017, 6:52 pm   #103
gazrawly
Tetrode
 
Join Date: Feb 2017
Location: Bristol, UK.
Posts: 60
Default Re: Sony HP-511 - Blowing Fuses

Thanks once again guys, you're keeping me sane here!

Nil carborudrum illigitimus is more than apt, made me chuckle...

The readings that I have from all of the driver transistors across E & B with set running on a Lamp Limiter, DMM set to 200v;

0507 2SC1124
at set switch on 16v rising to a peak of 23.0v

0508 2SA706
at set switch on 28.5v decreasing to a peak of 22.9v

0608 2SA706
at set switch on 27v decreasing to a peak of 21.6v

0607 2SC1124
17v rising to a peak of 23.1v

This differentiating voltage seem to be well above the 0.6v switch on? It seems overkill infact? The higher switch on voltage from the 0508 and 0608 seems a cause for concern? It didn't 'feel' quite right to me and at that moment, the Lamp Limiter glows quite brightly and then dims down within a second or two. I have a gut feeling that this has a relation to the readings...

Hope this makes sense to you guys.. Bad capacitor?

Q5 craic attached

Schematic here https://drive.google.com/open?id=0B1...XpNQU9qRHZPZXc



Gareth
Attached Thumbnails
Click image for larger version

Name:	craic.jpg
Views:	158
Size:	80.6 KB
ID:	141954  

Last edited by gazrawly; 1st May 2017 at 7:03 pm.
gazrawly is offline  
Old 1st May 2017, 7:22 pm   #104
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: Sony HP-511 - Blowing Fuses

You need to measure the voltages for all the transistors and all their E,B,C connections, eg: the emitter, base and collector voltages for Q504 through to Q510, which is supposedly the bad channel, then do the same for the good channel, eg: the emitter, base and collector voltages for Q604 through to Q610.

By doing the above you can compare the bad channel to the good channel in test voltage terms.

All measured with respect to the -ve supply rail.

Lawrence.
ms660 is offline  
Old 1st May 2017, 7:37 pm   #105
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,803
Default Re: Sony HP-511 - Blowing Fuses

To 'read' that amplifier, looking at the second bit of diagram Andy posted just above.

Q604 is in a sort of comparison circuit. It's base voltage is DC biased to somewhere about half the supply voltage by something off the picture feeding R651. An AC coupled signal is added in through C651. So the base voltage of Q604 is about half of the supply voltage and wobbles with the signal. Its emitter voltage is set by a complicated mess of resistors and capacitors, but if you look, R660 is the only DC path to the emitter because all the others lead through capacitors. So the DC level the emitter sits at is the DC level of the output of the power transistors... the other end of R660.

Q604 steers the whole of the rest of the amplifier to make its emitter about 0.6 or 0.7 volts more positive than its base voltage. If the output goes a bit too high, it turns on Q604 a bit more. If the output voltag is too low, Q604 turns off a bit. It's a balancing act called negative feedback. Q604 floats around and amplifies the difference between a scaled-down version of the output signal (scaled by R660 driving into R654.C653 means that the DC voltage isn't scaled, only the AC signal) and the input signal.

If the scaled down version of the output signal is kept equal to the input signal, then the output signal is being kept larger than the input by the inverse scaling factor.

Q606 does thehard work. It provides ost of the voltage gain and has todo all of the voltage swing. Q606 is turned on more or less by the changing current from Q604 driving its base. Q606 can't provide all of the current needed to drive the speaker, but it does have toswing all of the voltage. Q607 and Q609 are two successive current booster stages called emitter followers. They don't amplify the voltages, but they provide an awful lot of aplification of current. This is the heavy lifting department. Q607 and Q 609 can only carry current from the supply to the output. But we need toboth push and pull current to the speaker. This is where Q608 and Q 610 come in, these do the heavy work when the output voltage needs to swing downwards and current needs to be pulled from the speaker.

We've overlooked Q605. The output emitter followers each take about 0.6 to 0.7 volts to get them going. Q605 acts as a voltage dropper to put a bit of voltage difference between the bases of Q607 and Q608. Without this, there would be a bit of a gap in the middle while the voltage from Q606 swung across a dead-zone. Q605 keeps the output transistors always turned on a bit so they are running and ready for whatever they have todo.

R665 and R666 act to stabilise this standing current, and Q605's circuit artfully uses the transistor to temperature compensate it.

So that'syour amplifier dissected. Input stage, Voltage amplifier stage, and emitter follower output stage. And the bias transistor Q605 is usually called a Vbe-multiplier.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 1st May 2017, 9:49 pm   #106
gazrawly
Tetrode
 
Join Date: Feb 2017
Location: Bristol, UK.
Posts: 60
Default Re: Sony HP-511 - Blowing Fuses

Thanks for taking the time to write that David, I will try and understand this a little better with some more time...

Can you just confirm that basically everything that has Q/05** or C5** is the right channel and everything with Q/06*** or C6** is the left channel? Or have i got this completely wrong again? I can kinda work from there then and not bug you guys and gals too much.

How did they even come up with something as complicated as this in 1970?!!?

Gareth
gazrawly is offline  
Old 1st May 2017, 10:16 pm   #107
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,803
Default Re: Sony HP-511 - Blowing Fuses

It looks like Sony chose to number things like that. There is no standard way of doing it, but they're trying to be helpful.

Information and knowledge have a habit of breeding. Once you start to understand one bit, other things start to fall into place. I've been doing this sort of stuff for years and it takes a bit of doing to realise that what may seem obvious to me is new and strange to others. Don't try to force it, just let it sneak up on you.It's painless that way. Stop and look back at the way you've come. You can do a lot more now than you could a few months ago.

They were making much more complicated things in 1970, but all complex electronics amount to numerous repeats of fairly basic circuits, all flying in formation. At most you need to comprehend the general pattern, and then look at the details of individual circuits. You don't have to swallow the whole thing at one go.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 1st May 2017, 11:06 pm   #108
gazrawly
Tetrode
 
Join Date: Feb 2017
Location: Bristol, UK.
Posts: 60
Default Re: Sony HP-511 - Blowing Fuses

The Q5 / Q6 tagging is handy... The Q5's appear to be Lch, hope this is the knowledge breeding occurring!

What is the most complicated early 70's set you've worked on David?

I'll get back onto this when I can..

Thanks again people

Gareth
gazrawly is offline  
Old 1st May 2017, 11:29 pm   #109
RojDW48
Nonode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 2,074
Default Re: Sony HP-511 - Blowing Fuses

Quote:
Originally Posted by Radio Wrangler View Post
Stop and look back at the way you've come. You can do a lot more now than you could a few months ago.
I was talking to Gareth this afternoon and saying pretty much exactly that! Thanks David.
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline  
Old 2nd May 2017, 5:31 am   #110
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,803
Default Re: Sony HP-511 - Blowing Fuses

Complicated things I've worked on from the early 70's...

The early 70's for me started with working at Rolls Royce in Filton and the most complex thing I worked on was the Olympus 3-shaft jet engine. They're fairly complex beasties, but operate on simple principles.

My AR88 is World War 2 technology and a lot more complex than a music centre.

My Racal RA117 dated from the late fifties/early sixties and was definitely more complex than the AR88.

I've repaired and restored Quad 33 and 303 hifi amplifier systems which are late 60s technology for the domestic market.

Probably the most complex thing I've worked on from the late sixties is a GEC RC410 receiver.

The most complex thing I've worked on from the early 70's was the Marconi H2900 receiver

In the middle 70s I was part of the design team of the Hewlett-Packard Baseband Analyser 3724A 3725A and 3726A were the model numbers of the thee boxes which made it up There's an article describing it in the Hewlett-Packard Journal of April 1982.

For 1980s technology, the most complex thing I've worked on has been the HP8566B spectrum analyser.

1990s technology? Probably a mobile spectrum management receiver system I did for the German regulatory authorities. It combined an HP spectrum analyser with an Icom R9000 receiver.

If you were to look up the circuit diagram of that Quad 303 hifi amplifier, you would see that it's got a lot more parts per channel than your Sony, but once you find your way around it, you'll find it has the same structure. You'll recognise the input transistor comparing the input with the feedback. There's the voltage amplifier stage and then there are the current boosting stages. You'll also find the Vbe multiplier circuit.

If you look up any of these things and delve inside they'll look scary but they have structures that can be understood. The general block diagrams are straight forward, and the circuitry in each block is manageable. You just don't have to think of it all at once in detail. Otherwise no-one could handle them.

As far as complexity goes, I got shoved in the deep end, but I'm still afloat!

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 2nd May 2017, 6:07 am   #111
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,639
Default Re: Sony HP-511 - Blowing Fuses

Sorry, I got confused there, attached below are schematics of dodgy channel again.

David's description of your amplifier helps a lot, I can't read schematics like he can, only little bis. I understand what he's saying and will try to put it in even simpler terms for Gareth.

An amplifier makes your music, lets call it a signal louder and hopefully does this with "colouring" the sound. It should be a straight wire with gain.

There's two ways of doing this 1) by making a signal's voltage bigger, so 1v in 10v out 2) by making a signal's current bigger IE 10mA in. 1A out.

Transistor amplifiers does both. Firstly it boosts the signal's voltage in the preamp section, then a bit more in the power amp's driver section and finally those big Q's boost the current so it can drive a speaker.

Your amplifier isn't that complicated, only seems so. Back to your readings they don't make sense. There should be less than a volt between base and emitter. Here's what you have to do. First clip your black lead of your meter to chassis. Then take readings like this -

First take a reading on C558 (2200u biggish cap) Then ..

Q501
B BE*
C
E
Q502
B BE*
C
E ... etc, to Q510. I've just noticed there is a series pass transistor regulator, so take readings for Q511 and Q 512 as well. That should be ok as the RCH is ok.

Now do the same for C 658 and Q601 to Q610. Then take the black lead off the chassis, put your black probe on Q501's base and your red lead on it's emitter, take a reading and go and do Q501 to Q510 base and emitters and Q601 to Q610 base and emitters *. Be careful, a slip with a probe can short something and cause damage.


That should tell you where the problem lies. Should do, but may not.

Take readings after your amp has warmed up, say after 5 - 10 minutes. Only work on your amplifier when your fresh and in a good mood, never when tired or grumpy. If you start getting hacked off with it, switch off and walk away.

BTW, thought you were going over Roger's on Sunday? Don't forget Dave's offer of help to if you get stuck.

Andy.
Attached Thumbnails
Click image for larger version

Name:	Screenshot from 2017-05-02 05-12-03.jpg
Views:	125
Size:	88.7 KB
ID:	141985   Click image for larger version

Name:	Screenshot from 2017-05-02 05-16-15.jpg
Views:	145
Size:	91.0 KB
ID:	141986   Click image for larger version

Name:	Screenshot from 2017-05-02 05-31-27.jpg
Views:	122
Size:	79.7 KB
ID:	141987   Click image for larger version

Name:	Screenshot from 2017-05-02 05-15-33.jpg
Views:	327
Size:	112.3 KB
ID:	141988  
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline  
Old 3rd May 2017, 10:57 pm   #112
gazrawly
Tetrode
 
Join Date: Feb 2017
Location: Bristol, UK.
Posts: 60
Default Re: Sony HP-511 - Blowing Fuses

I have taken readings from the Left (faulty) power amp board and there is a clear issue here as we already know...

C558 2200uf cap 23.1v (other pin measured -00.0v)

Q504
E = 19.7v
B = 17.0v

Q505
E = 23.6v
B = 23.5v

Q506
E = 00.5v
B = 00.0v (with an occasional - flash short on DMM)

Q507
E = 23.1v
B = 23.6v

Q508
E = 23.1v
B = 23.4v

Q509
E = 23.1v
B = 23.1v

Q510
E = 00.0v
B = 00.0v (with an occasional - flash short on DMM)

Q511
E = 00.5v
B = 00.0v (with an occasional - flash short on DMM)

Q512
E = 16.0v
B = 15.4v

I will try and measure the other channel tomorrow. Some of the transistors are very small and I am having to turn the set off to test each individual leg making it very time consuming.

Andy, I decided not to bother Roger as we'd already ruled out the preamp board using Michael's Tape monitor method to bypass the preamp circuitry.. I've spoken to Dave and am just waiting for a time when he's free to look at the set for me.

Gareth
gazrawly is offline  
Old 3rd May 2017, 11:08 pm   #113
RojDW48
Nonode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 2,074
Default Re: Sony HP-511 - Blowing Fuses

Yes - it's all a bit beyond me now! I'm not even comfortable with PCBs, let alone those new fangled solid state devices. Valves and point to point wiring give me at least half a chance of solving a problem. Happy to offer support, tea and sympathy however whenever needed.
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline  
Old 3rd May 2017, 11:17 pm   #114
gazrawly
Tetrode
 
Join Date: Feb 2017
Location: Bristol, UK.
Posts: 60
Default Re: Sony HP-511 - Blowing Fuses

Roger, let me know when you get that sand filled speaker cab up and running and i'll join you for a tea. Hopefully this sodding Sony set will be going by then and we can chat about that too!

gazrawly is offline  
Old 4th May 2017, 6:13 am   #115
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,639
Default Re: Sony HP-511 - Blowing Fuses

Looking at your readings, which transistors do you think arn't working/are suspect considering all we've said? I'll give you a clue, one side of the OP isn't working.

What do you mean "(with an occasional - flash short on DMM)" ?

Your going to need to write down both right side and left and compare. I have a suspicion that you don't understand what I/we wrote. If your not sure ask.

BTW, your right, preamp is probably ok so you just need readings for Q504 - 510 and Q604 - 610.

Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline  
Old 4th May 2017, 8:06 am   #116
gazrawly
Tetrode
 
Join Date: Feb 2017
Location: Bristol, UK.
Posts: 60
Default Re: Sony HP-511 - Blowing Fuses

Ok so at the moment Q506 has no B and basically no E... that is turned on by Q504. So to me at the minute it could be either of those... the emitter on Q504 is far greater than the 0.7v suggested. Would an over voltage of the emitter pin on Q504 (compared to the voltage on the base) also cause Q506 to stay switched off? The other Qs emitter don't seem to be matching the 0.6v/0.7v difference or do these not have to?

Ignore the flash short comment, my incompetence at reading a DMM...

Gareth
gazrawly is offline  
Old 4th May 2017, 8:33 pm   #117
gazrawly
Tetrode
 
Join Date: Feb 2017
Location: Bristol, UK.
Posts: 60
Default Re: Sony HP-511 - Blowing Fuses

I have tested the other channel and have combined the results here;

+ve 46.5v (measured at smoothing cap)

C558 2200uf cap 23.1v

Q504
E = 19.7v
B = 17.0v

Q505
E = 23.6v
B = 23.5v

Q506
E = 00.5v
B = 00.0v

Q507
E = 23.1v
B = 23.6v

Q508
E = 23.1v
B = 23.4v

Q509
E = 23.1v
B = 23.1v

Q510
E = 00.0v
B = 00.0v

Q511
E = 00.5v
B = 00.0v

Q512
E = 16.0v
B = 15.4v

C558 2200uf cap 22.3v

Q604
E = 19.7v
B = 16.8v

Q605
E = 21.1v
B = 21.6v

Q606
E = 00.5v
B = 00.0v

Q607
E = 23.0v
B = 23.6v

Q608
E = 22.3v
B = 21.7v

Q609
E = 22.4v
B = 23.0v

Q610
E = 00.0v
B = 00.5v

So many questions. I was not expecting to see such a similar result from the array of Q's. I presume that Q504 & Q604 are operating within range and that the difference between the emitter and base is due to the amount of Q's it is adjusting to (in order to bring the voltage difference down, it must be multiplied to Q504 & Q604)? Hope that makes sense.

The right channel (Q6**) appears to have a better ~0.6v difference between emitter and collector. Some Q's have a greater emitter over base, while others have a greater base over emitter reading... If a difference of 0.6v is required on all the Q's then surely even the Right channel (the working channel) should not be working? Q605 has a difference of 0.5v between it's emitter and base.

I would suspect Q's 505 & 509 (possibly 508) given the limited deviation between emitter and base. But I am still unsure to tell you the truth. What is also worrying me is why the set blew Q's when it was plugged into the wall.

Dave has kindly got in touch and I'm hoping to get the set over to him Saturday.

Gareth

Last edited by gazrawly; 4th May 2017 at 8:55 pm.
gazrawly is offline  
Old 4th May 2017, 10:44 pm   #118
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,803
Default Re: Sony HP-511 - Blowing Fuses

In a normal transistor power amplifier, all the transistors should be turned on at least a little while idling. The only case of transistors turned off should be momentarily for the output current boosters when it is the turn of one side to do the work and the other side to turn off.

So Q504 has Vbe = -2.7v
and Q604 has Vbe = -2.9v

These are PNP transistors and should be reading -0.6 to -0.7 so I suspect you haven't been connected to where you think you have. Otherwise something is very wrong.

Q505 has -0.1 Vbe which means it is turned completely off there shouldn't be anything in the circuit here to make a negative voltage across here.
Q605 has +0.5v Vbe which looks like it's working it's an NPN type so the voltage is probably in the right ball park, but lowered by voltmeter errors.
Q605 and Q505 being around the 23v mark seems reasonable, though.



Q506 has -0.5v Vbe. there shouldn't be anything capable of making a negative voltage here. Are you sure you had the probes the right way round?
Q606 has the same issue.

Q507 has +0.5v which may be a little bit on.
Q607 has +0.6v which is good

Q508 has +0.3 Vbe which is the wrong way round for a PNP transistor and not enough to turn it on if the meter probes had been swapped.
Q608 has -0.6 which is the right polarity and about the right value.

Q509 has 0v which is off anyway you look at it
Q609 has +0.6v which looks good.

Q510 has 0v which is a definite off and might fit with Q508 being off.
Q610 has 0.5v which looks like a bit on.

So I'm afraid some of the readings look like the voltmeter might not have been connected where expected, even so some of the readings show a definite problem.

You need some hands-on guidance from someone experienced at this point. Transistor audio amplifiers can lead even fairly experienced people round in circles. I'm pretty sure that there is something wrong in one channel.

It's fixable, but you have to be very careful to measure everything right or else it sows confusion.

You're actually doing very well. It may not feel like it, but the experienced people have been through this phase, and there are plenty of experienced people on the forum who avoid such circuits.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 4th May 2017, 11:11 pm   #119
gazrawly
Tetrode
 
Join Date: Feb 2017
Location: Bristol, UK.
Posts: 60
Default Re: Sony HP-511 - Blowing Fuses

Thanks David, it's a steep learning curve as Andy said. I've tried my best to make sense of this. It must be the hardest thing i've ever tried to repair.

I must have the probes on the wrong transistor pins as I mirrored the pins from the Left channel onto the Right transistors. I used the schematics pictures to try and figure out which pins to apply the DMM to but the pictures were vague so I went with what appeared to be the correct 'front' face of the transistor (a 'cut off' on one corner of the transistor looked the same as the schematic sort of approach).

Even though this is more frustrating than I can put into words, I'm enjoying 'trying' to learn about this ridiculous mess of transistors in a weird way.

Fingers crossed that Dave can shine some light on the problem, I'm sure he can fit the DMM leads to the correct legs of the transistors, unlike myself! Ha

Gareth
gazrawly is offline  
Old 5th May 2017, 6:04 am   #120
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,639
Default Re: Sony HP-511 - Blowing Fuses

To me Q509 and Q510 look dead/suspect so I'd have them out and test them. but arn't they the one's you replaced? I'd test the electrolytic caps C556 and 557 and also test D501/2, but am sure you said you'd tested those.

I've only had moderate success with transistor amplifiers, and have been of the opinion that they are the spawn of Satan, invented by himself to turn budding audio tech's into gibbering vegetables. I keep a #5 tractor hammer handy by the bench lest they get too unruly. Valve amplifiers in comparison are, on the whole a leisurely pootle down the river with a fair maiden, our hands idly splashing in the water, a gentle breeze laughingly playing with our hair. : )

Whip Q509/10 out Gareth and give em a once over with your diode checker if you get time before popping round Dave's. If you have a couple of caps to try in place of C556/7 even better. If not hopefully Dave will as you say shed light ont subject.

Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 5:03 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.