Absolutely, but it's a beginning, right?
And i really like you use the word "we". Don't know yet if it's normal to be helped so much, i've never been a "forum guy". Here in Italy people are more jealous of their knowledge, mostly. I feel lucky.
And i really like you use the word "we". Don't know yet if it's normal to be helped so much, i've never been a "forum guy". Here in Italy people are more jealous of their knowledge, mostly. I feel lucky.
you better feel lucky right now because someday i just might figure out how to charge for troubleshooting via the internet! lord knows i could sure use the money!!!
Okay, I feel better, post #111 I said "check the two protectio n resistors are 1 kohm. "
When I come to Italy, no Globus bus for me. I'm sleeping on your apartment carpet.
I'm trying out an amplifier driver board today I hand built out of Nema C board. 27 components about 50 wires. Most of the wires are just component leads twisted together and soldered. The problem now is I saw a dot on a crossover of lines on the schematic where there wasn't one, and connected the base of the input transistor to 150 ohms to ground. DOH!. (head smack) The light bulb box and speaker capacitor caught it, probably no damage so far.
When I come to Italy, no Globus bus for me. I'm sleeping on your apartment carpet.
I'm trying out an amplifier driver board today I hand built out of Nema C board. 27 components about 50 wires. Most of the wires are just component leads twisted together and soldered. The problem now is I saw a dot on a crossover of lines on the schematic where there wasn't one, and connected the base of the input transistor to 150 ohms to ground. DOH!. (head smack) The light bulb box and speaker capacitor caught it, probably no damage so far.
Last edited:
Knowing Italians, he'll probably receive you with a little "antipasto" and Vermouth, while you wait for the main course 😉
An externally hosted image should be here but it was not working when we last tested it.
Ahahah Fahey is absolutely right!
And indianajo, you wouldn't sleep on the carpet.. I'll give you the royal guest room, no kidding. I wish you luck with the amp.
Turk, i could pay you with a lot of love and good energy if you like... 😀
I found a couple of 1 ohm resistors which are quite big. They wouldn't fit in the board unfortunately..
And indianajo, you wouldn't sleep on the carpet.. I'll give you the royal guest room, no kidding. I wish you luck with the amp.
Turk, i could pay you with a lot of love and good energy if you like... 😀
I found a couple of 1 ohm resistors which are quite big. They wouldn't fit in the board unfortunately..
I've been in a repair shop and i found some resistors which are slightly bigger in size, but they fit perfectly in the board, but they are not 1 ohm but 0.66 ohms.
Is that ok, what do you think?
Is that ok, what do you think?
at this point i'd be less concerned with the replacement resistors as i would be with the rest of the circuit (you have the amp running on "the dim bulb tester") i'd temporarily jumper the solder points of R22 R23 and check that everything is ok with the regulators and assuming that's ok seeing if the pre-amp board lives (remember we still don't know why this failed to begin with and it's possible there's still potential problems with the remainder)
due to your time factor i'd spend more time checking the rest than shopping for parts.
what wattage rating are the 0.66 ohm resistors?
due to your time factor i'd spend more time checking the rest than shopping for parts.
what wattage rating are the 0.66 ohm resistors?
I don't know, the tech didn't know.. Is there a clue to know that?
Could take a picture if that would help..
Could take a picture if that would help..
physical size and type.
some metal film flame proof types are quite small compared to old carbon composition resistors.
sorry i don't have a ready reference but you obviously have a working computer...so you can research that topic latter.
some metal film flame proof types are quite small compared to old carbon composition resistors.
sorry i don't have a ready reference but you obviously have a working computer...so you can research that topic latter.
Ok. So, before i burn something else, you give me the permission of making a bridge where the resistors were, and try to power on the amp? I could see if i got the famous -+15 v.
Meanwhile i search for the wattage of the resistors..
EDIT
it should be a 0.5 W one, against the original 0.25 W.
colour code says 0.51 ohm, i got around 0.6/0.7 with my DMM. at the tech place he measured 0.9 ohms..
in picture you can see both of them.
Meanwhile i search for the wattage of the resistors..
EDIT
it should be a 0.5 W one, against the original 0.25 W.
colour code says 0.51 ohm, i got around 0.6/0.7 with my DMM. at the tech place he measured 0.9 ohms..
in picture you can see both of them.
Attachments
Last edited:
i did mention keeping things on the current limiter for now if there is something like a hard short you'll know it the limiter lamp will tell you (to turn it off and start lookin' for the new problem)
ok to help your understanding can you figure out why i'm interested in the wattage rating of your replacement resistors?
ok to help your understanding can you figure out why i'm interested in the wattage rating of your replacement resistors?
Well, we don't want to burn them again, i guess.
Being lower in resistance means having more current on the circuit but less power dissipation trough the resistors themselves. Since the "new resistors" are more capable to dissipate power, we should be on the safe side. Question is if the increase of current would damage or dosturb something after the resistors.. I don't think, after all it's "just" some ohm decimals...
Is it right what i said?
Btw, the bulb limiter is obviously always there and i won't put it back until you tell me so.
Being lower in resistance means having more current on the circuit but less power dissipation trough the resistors themselves. Since the "new resistors" are more capable to dissipate power, we should be on the safe side. Question is if the increase of current would damage or dosturb something after the resistors.. I don't think, after all it's "just" some ohm decimals...
Is it right what i said?
Btw, the bulb limiter is obviously always there and i won't put it back until you tell me so.
not quite
think of the behavior of a fuse (which is what this is intended to replace) if you allow more current you can risk potential damage.
your not one of"those people" who thinks it's ok to just increase a fuse rating so it doesn't blow are you?
think of the behavior of a fuse (which is what this is intended to replace) if you allow more current you can risk potential damage.
your not one of"those people" who thinks it's ok to just increase a fuse rating so it doesn't blow are you?
Last edited:
Uh, I believe we are talking about 1 kohm protection resistors R22 and R23. And you are proposing to replace them with 0.66 ohms? I would not do that. 660 ohms maybe, but not 0.66 or a bridge. Blue Blue brown is 660 ohms, blue blue gold is 0.66 ohms.
One way of finding the component that blew the resistor at first is putting in some resistor smaller and higher wattage that won't allow the transformer to burn up. Then look for heat. I suggested a 47 ohm resistor, but I've never run into a transformer that weak.
Before I tried anything but a 1 kohm resistor of higher wattage, I'd replace all the electrolytic capacitors with new ones that will charge to > 100 kohms on a meter ohms scale. that includes the four on this board, and the 47 uf capacitor shown on the op amp board.
In series with a 660 ohm resistor you might even want a resettable PTC fuse like this one CMF-RL50A-0 - BOURNS - FUSE, PTC RESET, 220V, 50mA, RADIAL | Newark element14 US
or this one RXEF005 - TE CONNECTIVITY / RAYCHEM - FUSE, PTC RESET, 60V, 50mA, RADIAL | Newark element14 US
which are $.32 instead of $.006 but your time is worth something. These reset when the power is turned off and they cool down. They will pass 50 ma and go high resistance at 100 ma. The first is 11 ohm cold and the second is 50 ohm cold. If your shop doesn't carry them, farnell.com operates in Europe and is the owner of USA Newark.com
As a convenient source of things like 1 kohm resistors, I sometimes cut up old PCAT power supplies, or CRT displays, or old televisions, for the parts. The transistors ICs or tubes are not much use for audio, but the film capacitors diodes and resistors are usually fine. I keep these in plastic bags sorted by decade. I have an attic and don't move often, so storage is less of a problem here than in Europe, I suppose.
If the power board alone works fine (not tried yet) but too much voltage is dropped on the protection resistors by the op amp board, there may be a solder almost bridge that shorts only in wet weather, since the amp is fairly old. Op amps have pins very close together, and a little flux on the board can short if humidity gets too high. Hint, wash the solder side of the op amp board with alcohol.
The problem could be an op amp internal short, but this is rather rare.
Thanks for the kind response to my travel fantasy. That meal JMFahey pictured is also a fantasy, seen only in travel shows on TV, IMHO. USA Thanksgiving gatherings sometimes have as many dishes, but very different and less healthy food IMHO.
One way of finding the component that blew the resistor at first is putting in some resistor smaller and higher wattage that won't allow the transformer to burn up. Then look for heat. I suggested a 47 ohm resistor, but I've never run into a transformer that weak.
Before I tried anything but a 1 kohm resistor of higher wattage, I'd replace all the electrolytic capacitors with new ones that will charge to > 100 kohms on a meter ohms scale. that includes the four on this board, and the 47 uf capacitor shown on the op amp board.
In series with a 660 ohm resistor you might even want a resettable PTC fuse like this one CMF-RL50A-0 - BOURNS - FUSE, PTC RESET, 220V, 50mA, RADIAL | Newark element14 US
or this one RXEF005 - TE CONNECTIVITY / RAYCHEM - FUSE, PTC RESET, 60V, 50mA, RADIAL | Newark element14 US
which are $.32 instead of $.006 but your time is worth something. These reset when the power is turned off and they cool down. They will pass 50 ma and go high resistance at 100 ma. The first is 11 ohm cold and the second is 50 ohm cold. If your shop doesn't carry them, farnell.com operates in Europe and is the owner of USA Newark.com
As a convenient source of things like 1 kohm resistors, I sometimes cut up old PCAT power supplies, or CRT displays, or old televisions, for the parts. The transistors ICs or tubes are not much use for audio, but the film capacitors diodes and resistors are usually fine. I keep these in plastic bags sorted by decade. I have an attic and don't move often, so storage is less of a problem here than in Europe, I suppose.
If the power board alone works fine (not tried yet) but too much voltage is dropped on the protection resistors by the op amp board, there may be a solder almost bridge that shorts only in wet weather, since the amp is fairly old. Op amps have pins very close together, and a little flux on the board can short if humidity gets too high. Hint, wash the solder side of the op amp board with alcohol.
The problem could be an op amp internal short, but this is rather rare.
Thanks for the kind response to my travel fantasy. That meal JMFahey pictured is also a fantasy, seen only in travel shows on TV, IMHO. USA Thanksgiving gatherings sometimes have as many dishes, but very different and less healthy food IMHO.
Last edited:
Do not underestimate italians passion and care for food, never ever. They (we) are insane. I tell you again, and i'm really not joking, you've got a room in my house and if you plan to come in Tuscany, you really are wellcome. I live in a beautiful place, actually. Too bad people here is more involved in wine and chickens and not in audio gear.. 😀
Beside romanticism, the colours of the original resistor are: brown-black-gold-gold.
And that's a tiny 1 ohm. After all a fuse is actually in that range, isn't it?
Beside romanticism, the colours of the original resistor are: brown-black-gold-gold.
And that's a tiny 1 ohm. After all a fuse is actually in that range, isn't it?
Yes, I would put the brown black gold resistor (which is one ohm) in my 1 to 10 ohm storage bag, and not use it for R22-R23. You did ask for 1 kohm at the shop, didn't you? I suspect you are more of a musician than a detail person. That is one kiloohm, or brown black red. Sorry if the abbreviation didn't translate at first.
a 1 kohm resistor, on a 16 vac per side circuit, will drop 8 volts at 8 milliamp, which is not very much load current.
Sometimes (like in my RA-88a mixer) a resistor in the power lines is used to reduce hum in the op amps. (which is stupid but very cheap). My Ra-88a mixer had 330 ohms between the final e-cap and the op amps themselves, and when i removed it the mixer started humming worse.
Bert Wolf, a travel presenter on TV who lives in Memphis TN, filmed a very nice after harvest meal at a family winery in Tuscany. It was very pleasant just to look at.
a 1 kohm resistor, on a 16 vac per side circuit, will drop 8 volts at 8 milliamp, which is not very much load current.
Sometimes (like in my RA-88a mixer) a resistor in the power lines is used to reduce hum in the op amps. (which is stupid but very cheap). My Ra-88a mixer had 330 ohms between the final e-cap and the op amps themselves, and when i removed it the mixer started humming worse.
Bert Wolf, a travel presenter on TV who lives in Memphis TN, filmed a very nice after harvest meal at a family winery in Tuscany. It was very pleasant just to look at.
Last edited:
No man, i asked for 1 ohm.. There is another place i could go, the owner is a japanese wo worked for Sony in the '80s. He might have some spare parts.
Actually i don't know how and who said these resistors would be 1kohm.. If it was me, i really am sorry..
Actually i don't know how and who said these resistors would be 1kohm.. If it was me, i really am sorry..
well short of a better resolution scan of the documents i think it's 1 ohm because looking at both the silkscreen and schematic it still looks like 1R to me (different notation) but to me that says 1 ohm 0.25 watt or does my vision need retesting? in looking at the twenty one volt rail and the same scheme is employed there 0.22 @ 5W
Last edited:
- Status
- Not open for further replies.