Replaced the resistors for the same value new ones. Pulled the zener diode, measures good. I have continuity between all components so no cracked traces. Voltages the same or less.
Shall I take the switch board out to blast the switch better with cleaner? I get continuity through it though.
If it ain't the switch where do I get a transformer from? 13v.
Well appreciate your help guys 😁
Shall I take the switch board out to blast the switch better with cleaner? I get continuity through it though.
If it ain't the switch where do I get a transformer from? 13v.
Well appreciate your help guys 😁
It will still be all the same if you haven't replaced the standby transformer:
If the primary of the little transformer is open then you must replace it with something suitable... I linked to some earlier as I recall.
Don't go cleaning mains switches, they don't need it and you may disturb/wash away any montage grease used within.
If the primary of the little transformer is open then you must replace it with something suitable... I linked to some earlier as I recall.
Don't go cleaning mains switches, they don't need it and you may disturb/wash away any montage grease used within.
Indeed you did link a transformer, I apologise I missed the link. Surprisingly cheap too. I'll get one ordered soon, I'll just wait if I need more parts. Thank you very much Mooly, unbelievable help
Happy New to you all. All the very best.
I'll be fixing up the broken amps soon. The transformer in the link you kindly gave me Mooly it seems to have 2 legs on the primary. This one here has 3. I'm not sure if and how to wire that transformer and can't find one with 3 legs.
Thanks again
I'll be fixing up the broken amps soon. The transformer in the link you kindly gave me Mooly it seems to have 2 legs on the primary. This one here has 3. I'm not sure if and how to wire that transformer and can't find one with 3 legs.
Thanks again
Three legged primaries are fairly common but the part should really be as per the data sheet shown with that product... which does definitely show two leads.
So we can be sure, can you post a picture showing the markings/writing on the transformer, and also one showing the pins.
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Three pin primaries may be a split winding where the centre pin is used for 120V AC markets, or the third pin may be for mechanical stability only and not connected.
So we can be sure, can you post a picture showing the markings/writing on the transformer, and also one showing the pins.
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Three pin primaries may be a split winding where the centre pin is used for 120V AC markets, or the third pin may be for mechanical stability only and not connected.
I wasn't sure... you meant the old transformer, not the new 🙂
So that middle pin looks to be just floating on the old one. There is no print or connection to it. It may or may not have an electrical connection internally to the primary winding but that is of no consequence here.
Your new transformer primary just connects to those outer two pads (live and neutral). Check with your meter to be 100% sure you have continuity from those points to the mains plug.
Keep looking at the data sheet to familiarize yourself with the connections.
The secondary of your new transformer has two separate secondary windings (look at the data sheet). The black dots are called 'phase' markings.
When you wire the secondary you do it as follows.
1/ Use a sharp craft knife to cut the print as shown and remove a decent piece of the copper print to isolate the track.
2/ Add a wire link as shown. This has now wired one of the new primaries to your circuit and it should now work. Test the amp in this condition. See if the 13 volts DC rail is now correct. Is it high or low ?
3/ Assuming its all OK we now need to measure the DC voltage across R524 (the 47 ohm) when the relay is on and decide whether to add the second secondary winding in parallel to the first.
So that middle pin looks to be just floating on the old one. There is no print or connection to it. It may or may not have an electrical connection internally to the primary winding but that is of no consequence here.
Your new transformer primary just connects to those outer two pads (live and neutral). Check with your meter to be 100% sure you have continuity from those points to the mains plug.
Keep looking at the data sheet to familiarize yourself with the connections.
The secondary of your new transformer has two separate secondary windings (look at the data sheet). The black dots are called 'phase' markings.
When you wire the secondary you do it as follows.
1/ Use a sharp craft knife to cut the print as shown and remove a decent piece of the copper print to isolate the track.
2/ Add a wire link as shown. This has now wired one of the new primaries to your circuit and it should now work. Test the amp in this condition. See if the 13 volts DC rail is now correct. Is it high or low ?
3/ Assuming its all OK we now need to measure the DC voltage across R524 (the 47 ohm) when the relay is on and decide whether to add the second secondary winding in parallel to the first.
Attachments
Looking at the print (and I was just playing safe here) you don't need cut the track as long as that third pin from the left is not connected to anything. You do need the link though to connect pin 2 to the print.
Very intriguing. You don't half impress with your knowledge and detail you share among us here. Such a pleasure for many.
I feel confident I can get it working with your instructions. I'll order the part with others bits later tonight.
Well appreciate your help
I feel confident I can get it working with your instructions. I'll order the part with others bits later tonight.
Well appreciate your help
Thanks for the kind words 🙂
The important thing is just to take it slowly and check your work as you go along making sure everything goes where its supposed to.
The important thing is just to take it slowly and check your work as you go along making sure everything goes where its supposed to.
Well Mooly I finally got around to ordering the transformer, I ended up ordering the same one from RS and picked it up yesterday.
I followed your instructions with the link wire, I used solid core mains cable, sanded down the track, added a blob of solder to track and found the process very easy there. The new transformer is larger with the pin spacing far wider so struggled a bit to get in the holes yet managed and check for all continuaty, all good. I didn't cut the track.
Fired it with a DBT, leds on the front shown, relays clicked. Sweet smell of possible success lol. Checked voltages all was looking good. Tried headphones using my phone as the source, both channels worked well. Checked DC offset, all good. Wired speakers and works lovely, surprisingly good sound and bass power for a budget unit. Not on par with my Arcam Alpha pre and power amp set up yet not expected. I removed the DBT, same working condition 🙂
It took me a while to figure why other sources was not working and only CD direct, after going through the schematics for about an hour thinking the relay after the main processor was faulty I realised the advanced DA CD when switched turns other channels off and input pot is inactive. Never seen this before so blew my brain a bit.
I can't thank you enough sir, such a great help and definitely accelerated my learning experience here. 😁👍
BTW, the big mains transformer is a bit noisy, buzzing, yet not not going through the speakers so not worrying about it. I may drop it varnish one day if I get bored.
I followed your instructions with the link wire, I used solid core mains cable, sanded down the track, added a blob of solder to track and found the process very easy there. The new transformer is larger with the pin spacing far wider so struggled a bit to get in the holes yet managed and check for all continuaty, all good. I didn't cut the track.
Fired it with a DBT, leds on the front shown, relays clicked. Sweet smell of possible success lol. Checked voltages all was looking good. Tried headphones using my phone as the source, both channels worked well. Checked DC offset, all good. Wired speakers and works lovely, surprisingly good sound and bass power for a budget unit. Not on par with my Arcam Alpha pre and power amp set up yet not expected. I removed the DBT, same working condition 🙂
It took me a while to figure why other sources was not working and only CD direct, after going through the schematics for about an hour thinking the relay after the main processor was faulty I realised the advanced DA CD when switched turns other channels off and input pot is inactive. Never seen this before so blew my brain a bit.
I can't thank you enough sir, such a great help and definitely accelerated my learning experience here. 😁👍
BTW, the big mains transformer is a bit noisy, buzzing, yet not not going through the speakers so not worrying about it. I may drop it varnish one day if I get bored.
Great to hear that the new transformer has sorted things 
Buzzing on transformers is often caused by the incoming mains being slightly asymmetric and having a consequent slight DC shift away from zero volts. Have a read at this:
Mains DC and Transformers
Buzzing on transformers is often caused by the incoming mains being slightly asymmetric and having a consequent slight DC shift away from zero volts. Have a read at this:
Mains DC and Transformers
Thanks again.
This actually makes a lot of sense. I service a few PA amps with big transformers and they buzz too. Also noticed on a few hifi amplifiers before now.
I do think I also have a bad earth somewhere as I have a buzzing sensation when I rub my hand across a metal chassis, especially the faceplate and DAC chassis.
I use a mains filter extension socket yet whatever I plug into its the same.
This actually makes a lot of sense. I service a few PA amps with big transformers and they buzz too. Also noticed on a few hifi amplifiers before now.
I do think I also have a bad earth somewhere as I have a buzzing sensation when I rub my hand across a metal chassis, especially the faceplate and DAC chassis.
I use a mains filter extension socket yet whatever I plug into its the same.
That weird feeling in a fingertip as you rub it over powered up equipment is really common although you will struggle to find a definitive reason as to 'why' it happens. It is definitely not bad grounding as the same effect can be felt on old equipment with 2 core mains leads.