Recently bought a Dynatron SRX 80, need help with a few things!

[Mogga96]

Turns out it was 2 fuses Fixed that though

No, what I mean is there seems to be a lump in the way of 2 of the speaker tags, thus I can't connect them up. It seems like it's solder where the wire from the speaker itself joins onto the solder tags.

So what do I do to get around that?

[Edward Huggins]

OK, if you are going to use those speakers from the enclosures they are already in, you will find the tags under what you call a lump (looks like a large capacitor to me) which can be removed. However, if you do not wish to dissmantle these, you can easily search for: 6.5" 8 ohm full range speakers - online from Farnell, RS Components or Cricklewood Electronics. Your originals are twin-coned units, but you may have to settle for a standard cone. No real problem as the pull-out speakers are actually the mid/range tweeter units in your unit.

[Mogga96]

That "lump" has a white wire on it coming from the speaker itself to that tag. Will removing said lump effectively make it not work?

[Mogga96]

Left channel is completely gone, not sure if a fuse or what. Ohhh if I'd known a Dynatron was this troublesome I'd of gone for the Grundig I was eying up instead

It works through headphones only if the jack is plugged in half way, but only the left channel works. Push it in all the way, only the right channel works. Plugged the left speakers into the right channel and they work.

[Mogga96]

Well, I'm not correct there. It makes the right channel the left channel in my headphones if I have the jack only plugged in half way. It's not fuses either. So I think the channel on the amp is gone. Capacitor maybe? I have no idea, it's a little too hands on for my knowledge now.

Does anyone know repair places within the North East/Yorkshire area I'd be able to take it to? It's starting to get out of my depths now of what I can do to fix it.

[Edward Huggins]

The failure of one channel is very common on this the last series of Pye built Dynatrons such as yours that suffered from poor QC. Place a Post in the section on this site for Help/Repairs needed. There are many Members in your area.

https://www.vintage-radio.net/forum/...play.php?f=145

[Mogga96]

Originally Posted by Edward Huggins

The failure of one channel is very common on this the last series of Pye built Dynatrons such as yours that suffered from poor QC. Place a Post in the section on this site for Help/Repairs needed. There are many Members in your area.

https://www.vintage-radio.net/forum/...play.php?f=145

Cheers Edward, I've made a post there now.

Fingers crossed someone can give her life again

[dalgwcobl]

The SRX80 units were not Dynatron made; they were produced by a Philips set-up (which might even have involved Roberts) after the Dynatron factory closed. I believe the chassis is in fact a Loewe-Opta, and the speakers will most likely be Philips. The original Dynatron models did, indeed, used 8" x 5" downward-facing units and 4" x 3" tweeters in the pull-out sides.
If I remember correctly, in models with the higher-output amplifiers, the 8" x 5" speakers were 16 ohm, so that the amplifiers produced less power to avoid overloading the speakers, which were not exactly hi-fi.

[dalgwcobl]

If the main speakers are working but the foam surrounds have died, which is a common problem with many speakers of that era, they will need to be re-foamed. There are people on eBay who sell a kit to re-foam speakers. You need to have exact dimensions to get the right kit - or the speaker brand and reference number. I was able to resurrect some little AR speakers using a re-foaming kit and it was most successful.

[Mogga96]

Hello, you might recall a post from a couple of year ago regarding a Dynatron SRX 80a with a faulty output and blown speakers.

That was mine, I've nursed it somewhat back into health with replacing one of the internal fuses for the channel that wasn't working and was able to listen to my records again via headphones no problem until I get around to replacing the speakers.

However, the other night I had one of the rear fuses blow and it's back out of commission with no power.

The fuse that has blown going by the rear panel states a T800mA fuse and upon pulling out the fuse, it's an F800mA.

Has it been using the wrong fuse, thus leading to it having issues as such?
I've found both the T and F800mA fuses on RS Pro, but now I'm unsure if I definitely need to order a T or an F800mA fuse. Feel pretty silly considering the panel clearly states T, but it's been running on an F.

The tape deck I know is using a T800mA fuse, I tried taking that fuse out of the tape deck and with the tape deck completely disconnected, using that T800mA fuse but still no joy for it returning to life.

So what do I need? It was working fine with the F800mA fuse before it blew.

[peter_sol]

Did the temporary T800ma blow?

[Mogga96]

Originally Posted by peter_sol

Did the temporary T800ma blow?

It didn't, it wouldn't even power up with the T800ma fuse from the tape deck. Starting to think this might be a bit of a lost cause.

[Mogga96]

Uh so I took a gamble and ordered some T800ma fuses last night from RS Pro. They came this morning, put one in the back where the blown fuse was and it came straight to life.

Now it's up and running!

Only issues still needed to be fixed are:
Hum when touching the tonearm/turntable platter
Recone/replace downward firing speakers
See if there's a way to increase the signal the radio gets

Otherwise, everything is now spot on with it.

[Radio Wrangler]

A T type fuse means "Timed" they are designed to allow surges such as at turn-on when reservoir capacitors are charging. Normal fuses are much faster acting and much more easily pop on turn on.

So if it had an 800mAT fuse, and you replaced it with a fast one, fuse blowing isn't surprising.

David

[Edward Huggins]

Originally Posted by Mogga96

Uh so I took a gamble and ordered some T800ma fuses last night from RS Pro. They came this morning, put one in the back where the blown fuse was and it came straight to life.

Now it's up and running!

Only issues still needed to be fixed are:
Hum when touching the tonearm/turntable platter
Recone/replace downward firing speakers
See if there's a way to increase the signal the radio gets

Otherwise, everything is now spot on with it.

1: Check the turntable earthing or there may be an earth loop.
2: These are quite small speakers and it may not be possible to source cones of this size. Far easier to replace both units.
3: What type of FM aerial are you using now?

[Mogga96]

Originally Posted by Radio Wrangler

A T type fuse means "Timed" they are designed to allow surges such as at turn-on when reservoir capacitors are charging. Normal fuses are much faster acting and much more easily pop on turn on.

So if it had an 800mAT fuse, and you replaced it with a fast one, fuse blowing isn't surprising.

David

That's what I'm saying, I'd bought it 3 year ago with that F fuse in it, it blew and tried to use the T fuse from the tape deck, which didn't work.
But then the T fuses I ordered from RS brought it back to life.

Currently though trying to work out what exactly some of the buttons on the front even do since I can't find a manual for it.

What is AFC and what exactly is the Muting button supposed to work on? I'm guessing AFC is for trying to help with locking in on an radio signal and the Muting is to mute headphones?

[Radio Wrangler]

Those buttons are for the FM radio function only and don't affect anything else.

AFC = automatic frequency control. It is an automated fine-tuning system. The radio quality is still best if you get the manual tuning spot on, but AFC lets it hang on better. Optimum use is to tune around with AFC off and then trim for least distortion on the sound, then put AFC on to hold it.

FM radios have limiter amplifiers in their intermediate frequency stages, making an awful lot of gain when there is no signal tuned. This amplifies the noise floor massively and the audio it makes is pure, very loud noise. Rather unpleasant. The muting system looks to see if there is any signal tuned above a threshold, when it switches on the audio feed to the audio amplifier section. If it finds no or not enough signal, it mutes the audio outputs to silence the noise.

With muting off, as you tune between stations you'll get noise loud enough to blow your head off. Most FM receivers have muting always on, and no switch. You'd only want to switch muting off if you wondered whether there was a tiny signal somewhere.

Most people leave AFC on and muting on. But try the AFC off manual tuning before putting AFC on - it's actually easier than tuning around with AFC on.

David

[Mogga96]

Originally Posted by Radio Wrangler

Those buttons are for the FM radio function only and don't affect anything else.

AFC = automatic frequency control. It is an automated fine-tuning system. The radio quality is still best if you get the manual tuning spot on, but AFC lets it hang on better. Optimum use is to tune around with AFC off and then trim for least distortion on the sound, then put AFC on to hold it.

FM radios have limiter amplifiers in their intermediate frequency stages, making an awful lot of gain when there is no signal tuned. This amplifies the noise floor massively and the audio it makes is pure, very loud noise. Rather unpleasant. The muting system looks to see if there is any signal tuned above a threshold, when it switches on the audio feed to the audio amplifier section. If it finds no or not enough signal, it mutes the audio outputs to silence the noise.

With muting off, as you tune between stations you'll get noise loud enough to blow your head off. Most FM receivers have muting always on, and no switch. You'd only want to switch muting off if you wondered whether there was a tiny signal somewhere.

Most people leave AFC on and muting on. But try the AFC off manual tuning before putting AFC on - it's actually easier than tuning around with AFC on.

David

Ah good to know, thanks for the detailed response!
There's a plastic silver circle that pops out next to the FM presets as well which I'm not exactly sure is for, any ideas on that one? It's got quite a long end to it.

I thought it's for tuning the FM presets but it doesn't fit into those, found a crosshead screwdriver is what I need to use to tune them, so that thing confuses me.

[Mogga96]

Originally Posted by Edward Huggins

1: Check the turntable earthing or there may be an earth loop.
2: These are quite small speakers and it may not be possible to source cones of this size. Far easier to replace both units.
3: What type of FM aerial are you using now?

1. The ground for the turntable is on fine, I'll look into it further tomorrow. Though I found if I touch the platter with one hand, it stops.

2. Yeah figured as much, though when Ive been looking online at replacement speakers like the full range ones you mentioned before, they only seem to have two speaker tags on them, unlike the 4 that are on the downard firing ones that connect up the pull out speakers to them. So a little unsure of what speakers I need to look for.

3. I assumed it has an internal FM Ariel, so nothing if it doesn't have one internally.

[Edward Huggins]

WRT the above:
1: Yes, the hum will reduce because you are "earthing" it when you touch it. Check the earthing again throughly.
2: I think these are 8" x 5" units and will have 2 connectors. Check the impedance as the ones in you Dynatron may be 15 ohms. From these speakers the wiring is taken off through a filter capacitor to the mid-range/tweeter units in the side pull outs.
3: There is a crude internal aerial in this for FM and you will really need a indoor "T" dipole external aerial, these cost about £2-00. The AM tuning (if fitted) will have its own ferrite rod inside and so does not need an external aerial.