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Old 5th Jul 2019, 5:39 pm   #1
cdm1christopher
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Default Quad FM1 questions

Hi all
I have a Quad FM1 tuner and trying to figure out a couple of things so any help most appreciated. First the aerial has thrown me a bit as it's just a coaxial TV aerial socket, so not sure how that works as I have never used coaxial cable as an aerial before. I have a homemade outdoor aerial and ground is connected to the plumbing indoors. This works fine on my Trio WS38 but does not work at all on this tuner, not even a hiss hum whine absolutely nothing so any pointers be great.
I have attached a photo of a capacitor I have not seen before. The white one in the photo. They look like resistors wirewound having 3 terminals 2 of which radiate from side of cap the other straight off the end. It is dual as it has 2 x 1000pf capacitance on the side terminals. The 3rd goes to chassis ground. Can these still be bought? If so what are they called? If not any suggestions on how to replace them. They read fine on a meter but that does not always mean they're fine so be good to replace them. But obviously need to figure out on how to get it to work before spending.
Thanks for reading and any pointers greatly welcome.
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Old 5th Jul 2019, 8:09 pm   #2
dave walsh
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Default Re: Quad FM1 questions

Hi Christopher and welcome. Sounds like you have rigged some sort of Short Wave Aerial previously. The coax socket does not indicate a coax "aerial" but a screened lead that goes to a [much higher frequency] FM/VHF aerial [as with a TV aerial]. To test for hiss or signals, you can just plug in a short length of coax cable and attach about 18" of wire to both the outer and inner conductors. Cheap and cheerful. That gives you a basic horizontal dipole. Nothing is crucial, you can just tape it together. Best to read up on aerials in general perhaps. If nothing is happening then it may be the tuner but trying to spot faults externally is [generally] not a very satisfactory approach to repairing and restoring.
What amplifier is the Tuner connected to? This may help others to advise further.

Dave W

Last edited by dave walsh; 5th Jul 2019 at 8:16 pm.
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Old 5th Jul 2019, 8:36 pm   #3
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Default Re: Quad FM1 questions

Those white items are probably ok unless you have proved them faulty. There are ía number of black moulded capacitors, these are likely to be faulty but may not be causing the fault you have.

To determine whatís wrong you need to do some testing, donít change components unless tested faulty, it usually leads to frustration .
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Old 6th Jul 2019, 10:39 am   #4
cdm1christopher
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Default Re: Quad FM1 questions

Hi. Thanks for replies.

Okay I'll try that see what happens although does not quite make sense to me why have a strap and wire separated on the coaxial plug which plugs into the tuner but wire the other ends together? Thought been easier just to have single input for aerial and one for earth as on most radio/tuners? Is that just Quad trying to be different?

I'm running it through Quad Acoustic QC2 pre amp and the Quad Mono Block. Have run CD player through it but sounds awful I'm assuming will need adapter to sort that out again not sure why an aux was just not added. Seems to me Quad made it incredibly complicated to use for some reason. To be honest I was expecting a top piece of quality kit but compared to my 1960 Trio Stereophonic WS38 receiver quality is nowhere near the same. I suppose that's why there are so many for sale.

The white caps test good but not always convinced that means there not leaking or causing noise. I was curious as to what type these are as previously said never come across them before and they are dual 2 x 1000pF with three terminals. The other caps all Hunts and casings falling apart off most of them although most test good and within spec. Most of resistors or out of spec by about 20/35%. All valves seem fine on my Taylor tester.
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Old 6th Jul 2019, 1:18 pm   #5
Nuvistor
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Default Re: Quad FM1 questions

Quad are doing the job correctly, which is expected. The half wave dipole Dave suggested is a tuned circuit at the frequency of the VHF/FM radio waves. The coax is the transmission line to feed the voltage induced in the dipole to the input tuned circuit of the Quad.
Some notes on a VHF dipole.
https://www.electronics-notes.com/ar...le-antenna.php

My description is very basic, other forum members will be more able than me to give a complete description.

The white capacitors are unusual but from what I can tell are used to decouple the heater circuit, by having it balanced Quad must have found some benefit.

Very surprised the Hunts capacitors are good, good ones at that age are rare, did you check them for leakage at their rated voltage?
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Old 6th Jul 2019, 1:39 pm   #6
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Default Re: Quad FM1 questions

It looks from the picture that the resistors should be 10% (silver band) so you will probably have to change most of them. Those Hunts caps are well known to fail and probably did from a leakage point of view many years ago. As a repair man we changed most Hunts caps back in the 1960’s. The white ones are ceramic and will almost certainly be good for another hundred years or more.
Be very careful changing any parts to get them exactly where the old part was as poor positioning will affect the alignment.
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Old 6th Jul 2019, 3:06 pm   #7
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Default Re: Quad FM1 questions

Quote:
Originally Posted by Nuvistor View Post
Those white items are probably ok unless you have proved them faulty. There are ía number of black moulded capacitors, these are likely to be faulty but may not be causing the fault you have.

To determine whatís wrong you need to do some testing, donít change components unless tested faulty, it usually leads to frustration .
This is sound advice.

Yes, Hunts 'Moldseal' paper-dielectric capacitors of that age are probably 'leaky', meaning, like a leaky tap washer, they now drip through a little DC current instead of stopping DC altogether and only passing AC. That may not matter much in the circuit of your tuner, and would be most unlikely to stop it working.

Similarly, those attractively colour coded Erie resistors, highly regarded in their day, are likely to have increased their resistance value over the years. Again, that may not matter much, and is most unlikely to cause a major fault. Many resistor values chosen by designers are pretty arbitrary, so that a bit of drift in value with age may still be OK.

If your tuner is silent, I'd be starting with the basics such as: do the valves light up/heat up. Is the HT voltage present?

Best of luck,
Martin
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Old 6th Jul 2019, 5:48 pm   #8
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Default Re: Quad FM1 questions

The last FM1 i worked on had open circuit decoupling capacitors on the First IF amplifier the resulting measurements were great for DC but no gain at the IF was the result, from memory it was a black Hunts.

Trev.
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Old 6th Jul 2019, 8:46 pm   #9
dave walsh
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Default Re: Quad FM1 questions

Hi Christopher I think you misunderstood what I said. By "just tape it together" I meant that you didn't need to use connectors or solder connections, simply to try it out, just any sort of tape that was handy. It would indeed be silly to separate the the core [signal wire] in the the coax cable from the outer [the earthed screen] and then join them together [shorting any signal to earth] result zilch!...but that's not what I suggested.

As Nuvistor, said higher frequencies require different handling and the signal needs to be screened on its way to the Tuner. The idea [at the aerial end] is to make one by cutting about a yard of wire in two, connecting one piece to the screen and one to the core [not electrically strapping them together] and that's your dipole aerial There are other means of matching the impedance of the Tuner to the centre of a dipole aerial but coax is more convenient eg for TV/Hi-Fi usage. Once you've read up and seen a dipole diagram it should be very clear. It's all on the InterWeb these days anyway. Years ago we had to haunt the Library in the hope of maybe finding a book or article with relevant information that could be applied methodically.

Dave W

Last edited by dave walsh; 6th Jul 2019 at 9:10 pm.
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Old 8th Jul 2019, 2:18 pm   #10
cdm1christopher
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Default Re: Quad FM1 questions

Hi all
well I decided to clean the unit in a bath of isopropyl alcohol and the oil that came off was phenomenal not sure why it was saturated like that. I then connected a new signal lead and then made aerial as Dave suggested and bingo got reception none of the resistors or caps went up in smoke left it on for 3 hours so was surprised there. So question begs is it worth changing everything? From financial point of view these units don't seem to be worth much so would I be throwing money away?
Big problem again volume gain weak and very distorted exactly the same as the cd player although I think the input of cd is much higher than recommended. But because the tuner is doing the same obviously something wrong somewhere. The filters, bass treble all working fine.
I have completly renewed everything in the qc2 and the quad 2 including a brand new choke. All resistors have been replaced with 2 watt and the higher wattage with 10 watt. All caps replaced with polys rated 630v and the polystyrene rated 600v. I did replace the oil caps for cheap russian oil caps rated at 1000v so not sure if they are causing a problem. Replaced snubber on qc2 volume with x2 but the resistor rating is 100r whereas original rated at 220r so again not sure if that's causing the problem. Looked at Keith's page but he does not really cover the qc2 and to find any detailed info seems non existant. Plenty on the newer pre amp. Plus new valves apart from the KT66 but they tested very good on my taylor tester although so did the rest. Couple starting to get bit tired. Anyhow at least I've got tuner working.
Sorry guys digressed there so it's off to drawing board and try to work out what's wrong although having changed everything gonna be a challenge. Golden rule change abit at a time test continue unfortunately I went gun ho.
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Old 8th Jul 2019, 2:31 pm   #11
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Default Re: Quad FM1 questions

First step: try your CD player and tuner into a different amplifier.

If they then sound OK, focus on your QC2 pre-amp. It's possible that your CD player is simply overloading the QC2 (domestic audio signal levels increased with the advent of CD) , though that's unlikely to be the case with the tuner, which is presumably designed to work with the QC2.

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Old 8th Jul 2019, 3:02 pm   #12
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Default Re: Quad FM1 questions

Quote:
Originally Posted by cdm1christopher View Post
Golden rule change abit at a time test continue unfortunately I went gun ho.
Evaluate and then testing to find the fault is the golden rule, only diversion is if there are known components that can cause damage.

Glad the tuner is working, until you sort out what appears to be a fault on the pre amp you won’t know how well.
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Old 8th Jul 2019, 4:26 pm   #13
cdm1christopher
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Question Re: Quad FM1 questions

Cheers Guys theres no problem with cd as for tuner not sure I want to be playing around with HT to test on my other equipment as they don't have same lead connections.
I think as mentioned prob pre amp might start with those Russian caps. Ha I think it's going to be a long haul oh dear
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Old 8th Jul 2019, 8:00 pm   #14
cdm1christopher
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Default Re: Quad FM1 questions

Well guys I have some serious issues going on here.
I know at one stage I left the mono block on for about 10 minutes before realising I had no load attached.

I think the mains transformer is knackered or on it's way out.

Mains transformer
no power on 240v pin.
HT 5v?
5V reading 375v
6.3v no reading

Choke
373v
capacitor/resistor side 22v

Smoothing caps positive both read 374v

Output transformer
Z&X 376v
Y 374v

GZ34
Pin 1 375v
pin 4 5v

KT66 both valves
pin 2 5.2mV
pin 4 363v
pin 6 363v

EF86 both valves
pin 1 97v
pin 6 363v

So do you think I have knackered mains transformer?

That explains the bad distortion on volume me thinks way to much voltage. So definitely is not the pre amp.

Any ideas?

Cheers Chris
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Old 8th Jul 2019, 8:26 pm   #15
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Default Re: Quad FM1 questions

Have you a circuit?

You have 374 volts on the smoothing cap, what makes you think the mains transformer is faulty?

Edit. No power on 240 volt pin, are you running the amp on the 220 v tapping and nothing works if using the 240v tap?
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Old 8th Jul 2019, 9:02 pm   #16
cdm1christopher
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Default Re: Quad FM1 questions

Readings seem to be all wrong. Looking at schematic. HT should be 330v reading-5v on transformer. The 5v on transformer reading 375v? and no current at 6v on transformer 0v? Then readings on valves are way out. I'll need to check properly tomorrow find exact values for valves.
Yes readings using 240 as posted but if you switch to 220 then voltage goes over 400v.

Did rush did not measure any drops across resistors except on choke where you have I think it was 22v one side then 0v other side. Unless I have wired up the new choke wrong way round?

Yes there is a circuit had tuner and cd player running through it all but a lack of volume plus high distortion and hum has become much more noticable.
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Old 8th Jul 2019, 9:16 pm   #17
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Default Re: Quad FM1 questions

I have got a circuit from Keith Snooks web site, whether itís the same amplifier as yours I donít know.
The voltages on the EF86 Pin 6 anode is very different, can you check this again?
The KT66, pin 2 is a heater pin.
Pin 4 is G2 screen grid
Pin 6 is not connected to the valve, is it used as a tag for something else?
Output transformer voltages are a bit high but OK for now.
Can you check the anode voltages of the KT66?

Can you explain the voltages in your list for the mains transformer, I think you may not be taking the measurements correctly.
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Old 8th Jul 2019, 9:19 pm   #18
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Default Re: Quad FM1 questions

Perhaps nothing to do with this but the input to the amplifier is DC coupled, if the feed as a DC voltage on it that will upset the input stage, something to keep in mind when you have sorted out the voltages on the power amp.

I have not worked on any Quad amps so I can only go off the circuit I have, it is hopeful the same as your amplifier.
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Old 8th Jul 2019, 9:41 pm   #19
cdm1christopher
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Default Re: Quad FM1 questions

Cheers Frank
same here never worked on one before and was going by Keith's voltage readings which were not all tallying up but as said was rushing using torch to see pin numbers as getting dark so prob got numbers mixed up. I'll have a proper take your time check tomorrow.

Cheers Chris
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Old 10th Jul 2019, 1:25 pm   #20
cdm1christopher
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Default Re: Quad FM1 questions

Hi Frank
must admit bit confused by schematics.
now on T1 there is a P connector not listed on schematic. Now r10 is connected to this plus pin 2 on ef86 which is also connected to negative on C5 plus R12.

Now also all pins on ef86 are all linked for contuniuty except pin 7.

Now SK2 and SK3 all showing continuity r s t q.

I've moved SK3 straight to chasis ground on pin 1 on SK1. was mild improvement in loudness and slightly less distortion. But not pleasant to the ear.

Bit baffled I'm going to test these dc ratings and see if any tally up.

Main problem I have is none of the valve pins are marked on schematic so making it difficult as I'm tooing and throwing between spec sheets for valves so can word out grid screen cathode etc.

Pretty new to this so takes time to learn.

Cheers Chris
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