The tape input should work just like all the others. There is a tape monitor switch as well as the normal input selector switch so make sure you are feeding the signal in correctly.
The mains switch needs care. It may be sticking because the old 'montage grease' used when switches are assembled has hardened but you need to be careful how you go about it. Do not use anything like WD40 on mains contacts, you would need something designed for the job. A lot depends on what type of switch it is as well, whether a separate switch or part of the switch bank..
The Oscillation could be caused by a broken capacitor leg (or faulty cap), thats if your unit has this cap fitted! I have attached a pdf with the capacitor in question circled. This is one of the issues with these units-never are any two alike. They updated them as time rolled on but the modification info is not available.
If this is not the cause of your oscillation then I suggest following Mooly and Indianajo's advice.
good luck
If this is not the cause of your oscillation then I suggest following Mooly and Indianajo's advice.
good luck
Hi ric - I need to replace the speaker caps in my Armstrong 625 (the big blue electrolytics). I see you replaced yours. Please could you let me know where you got your replacements. Thanks.
Hi there - from Cricklewood Electronics in the UK:
| 3300C100 | 3300uF 100V Electrolytic Can Capacitor by Samwha | £5.50 | 1 | £5.50 |
| 4700C63 | 4700uF 63V Electrolytic Can Capacitor by Samwha | £3.00 | 2 | £6.00 |
Many thanks for your super quick reply ric - I finally got one of the caps out after an epic struggle of twisting it and whacking it - is there an easier way?
I see that the replacements are much smaller - how did you secure them in place?
I see that the replacements are much smaller - how did you secure them in place?
Not sure if there is an easier way to remove them - just desolder the connecting wires and clip the cable ties holding them in. To refit the samller, I cut some wine corks vertically in to half cylinders and use three to wedge the cap in to the larger hole. When I am satisfied I won't need to take them out for a while I'll use a spot of hot glue on them. Plus cable ties for the larger single cap to hold it on the chassis. Can send photo later.
wow ric - you are a genius! I have had dozens of old wine corks for years because I thought they might come in useful one day. At last!!
The smaller caps are not held in by cable ties but by metal spring clips that exert a ferocious grip. It says the Samwha caps have snap-in connectors - can I solder on to them?
Is the 3300 µF 100V Samwha capacitor to replace the smoothing capacitor (which is held in to the left-hand front corner by plastic ties)? I haven't removed the original one yet so I don't know its values.
The smaller caps are not held in by cable ties but by metal spring clips that exert a ferocious grip. It says the Samwha caps have snap-in connectors - can I solder on to them?
Is the 3300 µF 100V Samwha capacitor to replace the smoothing capacitor (which is held in to the left-hand front corner by plastic ties)? I haven't removed the original one yet so I don't know its values.
It's slightly fiddly to solder on to the as they are flat tabs and don't have holes to put the wire through first, so make sure you get a good connection. I dabbed some flux on to the pins first.
yes it's the smoothing cap in the bottom corner. I've seen different values quoted in chatrooms for this but in my case this was the original cap and clearly marked, and corresponds to value on the circuit diagram.
Hi ric
Unfortunately Cricklewood Electronics don't have the 3300µF 100V capacitor. They do have 3300µF 50V. The full circuit diagram isn't shown on the link you sent me above so I don't know whether that will be adequate. Do you know what the original values are for the smoothing capacitor?
Unfortunately Cricklewood Electronics don't have the 3300µF 100V capacitor. They do have 3300µF 50V. The full circuit diagram isn't shown on the link you sent me above so I don't know whether that will be adequate. Do you know what the original values are for the smoothing capacitor?
Thank you for the table. Jason reported that table-rendering had been fixed, and I am glad to see it. (AND to be able to Quote a table.)
Hi Guys - newbie here, seeking some advice on a fault on my 625's Z20 board. The ERG 47 ohm resistor (component 238 in the wiring diagrams) has burnt out - possibly as a result of me replacing the blown 125A fuse with a spare 2.5A (naughty!) to see if that was the problem.
I'm having difficulty in sourcing a replacement. I know it's a metal oxide type, 47 ohm, 75 volt, but I don't know what wattage. Can some kind soul help with a product code for an acceptable replacement?
Also, if the cause of the original fault was likely to be further down (or up-) line, where should I be looking. I know my way around a soldering iron, but my electrical knowledge is confined to knowing I should swap-out the burnt and blackened bits. I also have a multimeter and can follow simple instructions! 🙂
I'm having difficulty in sourcing a replacement. I know it's a metal oxide type, 47 ohm, 75 volt, but I don't know what wattage. Can some kind soul help with a product code for an acceptable replacement?
Also, if the cause of the original fault was likely to be further down (or up-) line, where should I be looking. I know my way around a soldering iron, but my electrical knowledge is confined to knowing I should swap-out the burnt and blackened bits. I also have a multimeter and can follow simple instructions! 🙂
Unfortunately, you'll have to go over the regulator circuits and locate the problem.
The regulated 45 volts is controlled by those two transistors, which could have crapped out.
Or any of the associated components could be at fault.
Sorry, but diagnosing things over the internet is not a sure way to do things.
Something like that would have to be on my service bench for me to give any certain answer.
The regulated 45 volts is controlled by those two transistors, which could have crapped out.
Or any of the associated components could be at fault.
Sorry, but diagnosing things over the internet is not a sure way to do things.
Something like that would have to be on my service bench for me to give any certain answer.
Bing can't find 625 schematics on the web. This thread: https://www.diyaudio.com/community/threads/armstrong-625-diagnosis.385711/
has a couple of screenshots but not the part you are looking at. No picture of the regulator board.
a 5 watt 47 ohm resistor would probably not burn out next time, if it is short enough to fit standing up.
People usually put a 60 w incandescent lamp bulb series the AC input to prevent fuses blowing while they take voltage measurements. I have my lamp socket in a grounded steel case so if a wire pops off I don't get burned, neither does the coffee table. AC receptical on case, a line cord, a 5 amp breaker on input, mesh cover to see the lamp light up complete the project.
I am not a pro and in winter will take time to look at voltages on a schematic and tell you which ones are out of line.
Don't use two hands to take voltages, >25 v across your heart can stop it. Use an alligator clip lead to speaker ground to the negative probe of DVM. Wear no jewelry on hands wrists or neck, 1 v at high amperage can burn your flesh to charcoal. Wear safety glasses, parts explode and solder splashes.
has a couple of screenshots but not the part you are looking at. No picture of the regulator board.
a 5 watt 47 ohm resistor would probably not burn out next time, if it is short enough to fit standing up.
People usually put a 60 w incandescent lamp bulb series the AC input to prevent fuses blowing while they take voltage measurements. I have my lamp socket in a grounded steel case so if a wire pops off I don't get burned, neither does the coffee table. AC receptical on case, a line cord, a 5 amp breaker on input, mesh cover to see the lamp light up complete the project.
I am not a pro and in winter will take time to look at voltages on a schematic and tell you which ones are out of line.
Don't use two hands to take voltages, >25 v across your heart can stop it. Use an alligator clip lead to speaker ground to the negative probe of DVM. Wear no jewelry on hands wrists or neck, 1 v at high amperage can burn your flesh to charcoal. Wear safety glasses, parts explode and solder splashes.
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Thanks for your input guys. Yes - diagrams and pics would have helped, so here's a couple;
The resistor I'm trying to track down is ringed red. See also a pic of the problem board. I've gone over all the other boards and apart from one in-line 50v 470mF cap (which has clearly blown) everything else seems OK as far as I can see. If I can find out what value that resistor is I'll order one up plus the cap and give it a go. If that fails then I either throw money at it or ebay it for spares/repair!
@indianajo - thanks for the advice on keeping AC at bay! 🙂
The resistor I'm trying to track down is ringed red. See also a pic of the problem board. I've gone over all the other boards and apart from one in-line 50v 470mF cap (which has clearly blown) everything else seems OK as far as I can see. If I can find out what value that resistor is I'll order one up plus the cap and give it a go. If that fails then I either throw money at it or ebay it for spares/repair!
@indianajo - thanks for the advice on keeping AC at bay! 🙂
Five watts?
That area is only using less than 200 mA, a ONE watt should suffice if the unit has no other issues.
The resistor 428 feed electrolytic capacitors noname 470 uf, C49 47 uf 449 450 451 452 . All of these are suspect of shorting at 50 years. I would replace all, with capacitors rated >3000 hours service life from a major distributor. Farnell, Cricklewood, RS, or digikey. Voltage should be 64 80 or 100 on the 470, 50 or 64 on the 22 uf & 47 uf ones. The current on resistor 428 is pretty high, 5 w rating may not be enough. I can't see how long 428 is from the picture, if 2" long buy a 10 w resistor. Make sure you mark the + on to board before replacing e-caps, they blow up if put in backwards.
Saving money on the resistor just buys you another $10 shipping charge from the distributor if it blows again. Buy more than one fuse. Those small wattage Vishay metal film resistors run 300 F at the rated wattage now, which will burn your board. You could perhaps get away with a 3 w, 160 ma across 47 ohms is 1.2 W.
Saving money on the resistor just buys you another $10 shipping charge from the distributor if it blows again. Buy more than one fuse. Those small wattage Vishay metal film resistors run 300 F at the rated wattage now, which will burn your board. You could perhaps get away with a 3 w, 160 ma across 47 ohms is 1.2 W.
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