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Silver Member Username: Joe_cOakwood, Ga Post Number: 853 Registered: Mar-05 | I just aquired a Jolida 502b nearly new and seem to have some trouble. The 8 ohm speaker connectors work fine on both channels, but the 4 ohm only works on one side. I tried different sources with no avail. Since I am new to this tube thing, can anyone point me in the right direction. I can perform minor service in the way of soldering and checking lines or connections with a multimeter. thanks in advance. |
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Silver Member Username: Joe_cOakwood, Ga Post Number: 855 Registered: Mar-05 | Hooking it up to the 8 ohm side though, it sounds magical. I only have Totem Rainmaker bookshelves so , correct me if i am wrong, this shouldn't harm the amp or speakers running off the 8 ohm speaker hookups. Of course I am not blasting it either. |
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Gold Member Username: Jan_b_vigneDallas, TX Post Number: 4854 Registered: May-04 | First of all, don't run a tube power amp without a load conencted. The amp will start to oscillate and eventually it can do serious damage to itself. If this is a new amplifier under warranty, I wouldn't open any of the case work. You could possibly void your warranty. Did you buy the amp from a dealer with a warranty? Is this a brick and mortar shop where you can ask them to open the amp and check for poor connections? |
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Silver Member Username: Joe_cOakwood, Ga Post Number: 857 Registered: Mar-05 | No warranty, slightly used, got it for 600. Runs great on 8 ohm. |
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Silver Member Username: Joe_cOakwood, Ga Post Number: 858 Registered: Mar-05 | I was reading this: For this reason, the argument that only speakers with an impedance of 8 ohms or higher will work on tubes is incorrect. There are many tube friendly speakers whose nominal impedance is 4 ohms. If the speaker's impedance is relatively flat and consistently hovers around 4 ohms, and if the phase angles are only slightly capacative, or better yet inductive, there is no reason why a 4 ohm speaker cannot perform well on a tube amplifier. Some of our favorite tube friendly speakers are 4 ohms! It is also important to recognize that one need not use the 4 ohm taps on a tube amp with 4 ohm speakers. Many 4 ohm speakers sound their best when hooked up to 8 ohm, or even 16 ohm taps. If the speaker presents a resistive load (i.e. the impedance is flat - even though it is low) the 8 or 16 ohm taps will work fine, and always sound better than the 4 ohm taps. If the speaker requires more current because the impedance is low and and not terribly flat, the 4 ohm taps will likely offer better bass control at the expense of definition in the highs and mids. We encourage you to try your speakers on each of the output taps and hear for yourself the difference. so maybe I am fine since it seems to be fine on the 8 ohm side got this info here:http://www.symphonysound.com/articles/tubefriendly.html |
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Gold Member Username: Jan_b_vigneDallas, TX Post Number: 4864 Registered: May-04 | The amp is useable but not OK. All taps should offer signal when connected to a loudspeaker. If there is no warranty and no possibility of exchange, open the case to check for bad solder joints. Since the 8 Ohm taps work, the problem would be from the lead out of the output transformer to the 4 Ohm terminal in question. It's as simple as that. Nothing else can be affecting the situation that you could solve. If the problem is in the transformer windings proper, the amp will require service. Unplug the unit and let it sit for at least 30 minutes before you stick anything into the amp. Tubes amps carry lethal voltages even when not powered up. If you know how to drain supply caps with a load resistor, this will allow you to work on the amp once the caps are drained. It can't be opened any longer, but this was one of my favorite web pages concerning DIY and repairing tubes; "Experiments in Electrocution: Ye DIY Pages". You do want to compare the sound quality of the various taps to decide which transformer tap will work best with your speakers and your taste. Read the "Tube Talk" thread for more information. https://www.ecoustics.com/electronics/forum/home-audio/119397.html Let me know what happens. |
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Gold Member Username: KeggerWarren, MICHIGAN Post Number: 2569 Registered: Dec-03 | All that info joseph is pretty much on. My bet if the 8 ohm taps are fine and 4 ohm has 1 channel gone it's probably the wiring to the 4 ohm tap positive on that channel is not conected internally and it would be a rather easy fix, simply reconnect the wire. The only other thing I can think of without seeing the unit would be the 4 ohm tap on that channels output transformer would be fried but I highly dought that. So I would open the unit up "after it sat for about an hour being unpluggeed and turned off" Still be very careful of what you are grabbing because even being off the caps will still hold a charge, one of the things to try and remember is keep one hand in your pocket and then be careful with the other hand but at least by keeping one hand in your pocket you are not making a path accross your body for the current flow. Anyway trace the wiring on both sides to the 4 ohm taps and try to find the point of disconection. |
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Gold Member Username: KeggerWarren, MICHIGAN Post Number: 2570 Registered: Dec-03 | Dam Jan you beet to it as I was typing while you were posting and both said basically the same thing so hopefully between our 2 posts Joe gets the idea! Later! |
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Silver Member Username: Joe_cOakwood, Ga Post Number: 859 Registered: Mar-05 | When you say OK is that refering to the fact that it's not 100% operational or will I do damage to the unit even at normal levels running on the 8 ohm taps. It seems like that article says I am ok but I do value your opinions. |
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Gold Member Username: Jan_b_vigneDallas, TX Post Number: 4873 Registered: May-04 | If there is a loose wire inside the amp that could touch a hot lead to a chassis ground, you could be in for BIG TROUBLE. I would not run the amp until you have made certain there is no potential for an expensive replacement of a shorted transformer. |
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Silver Member Username: Joe_cOakwood, Ga Post Number: 862 Registered: Mar-05 | Well, now it works. I opened up the bottom and folowed the 4 ohm wire which led to the transformer and thats where I stopped. I then wiggled all connectors within that path and also the caps, no problem. Don't know what was going on , but it's fine now. Thanks fellas. And OMG what a jump from the NAD, which is no slouch. |
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New member Username: Weller1979Post Number: 1 Registered: Aug-05 | hi there can any one help,,,i can not get my sony cd remote lead to work when i connect it 2 my kenwood 2 channel amp,, only time i get power on the amp is when connecting it 2 the power that go's 2 the car stereo,,then the amp comes on and go's off when i turn the car keys,,also i am only connecting 4 speakers up no sub can any 1 tell me the best way 2 connect them up,,thanks all |