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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Wed Jun 27, 2012 1:14 pm
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+1 on the Bias Tester....$80 well spent, and makes the process a cinch!


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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Wed Jun 27, 2012 2:18 pm
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One thing I've done on all DRRI and TRRI I've worked on is replace any generic PS caps with Sprague Atoms, Panasonic, or F&T caps. Panasonics are hard to find now (in 375-500VDC range). Anyhow, this really has helped the reliability of most of the amps. As does good tubes and proper biasing.


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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Wed Jun 27, 2012 3:00 pm
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shimmilou wrote:
Hou-Tex wrote:
On the tube biasing, where can I get one those testers, or is something I can build myself with the help of a EE at work?


You can build your own with a precision 1 ohm resistor, socket, and cable, using your own multimeter to measure DC mV drop across the resistor. The connection in the socket for the tube Cathode is broken and the resistor inserted in series with the Cathode. In the case of a 1 ohm resistor, mV can be directly translated to mA, and read with a DC volt meter.

There are probes on the EuroTubes site that you can buy.
http://www.eurotubes.com/eurotubes-Bias-Probe-Pro-One-current-watts-voltage.htm

The MQ10 from A#Fretworks is the one that I use.
http://www.asharpfretworks.com/5543.html

You can easily measure the Plate volts directly from the amp with a volt meter if you are careful, or you can get the probes that allow Plate voltage measurement through the socket adapter, options for either of the probe sets mentioned above.



Thanks. So basically it's just measuring the voltage drop between two pins. Which pins?

I have a DVM and some resistors laying around.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Wed Jun 27, 2012 3:15 pm
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A bias probe will have the 1 ohm resistor in series with the Cathode of the tube, read DC mV across this resistor, with probe and tube installed and amp on. The cable coming from the socket of the bias probe, is to connect a meter for the purpose of reading across the resistor. The resistor must be a precision resistor of usually 1% or 2% tolerance, in order to be accurate. Some people actually modify their amps to install the one ohm resistor on the amp itself, no probe needed in that case. You have to break circuit traces on the amp circuit board to install resistors. For the DC Plate voltage, measure from ground (chassis) to pin 3 of the output tube with the tube installed and amp on, it will be approx 400 volts DC. Measuring the Plate voltage can be dangerous as it is high voltage, the additional Plate voltage probe is just a safer way to measure the Plate voltage.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Wed Jun 27, 2012 3:27 pm
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shimmilou wrote:
A bias probe will have the 1 ohm resistor in series with the Cathode of the tube, read DC mV across this resistor, with probe and tube installed and amp on. The cable coming from the socket of the bias probe, is to connect a meter for the purpose of reading across the resistor. The resistor must be a precision resistor of usually 1% or 2% tolerance, in order to be accurate. Some people actually modify their amps to install the one ohm resistor on the amp itself, no probe needed in that case. You have to break circuit traces on the amp circuit board to install resistors. For the DC Plate voltage, measure from ground (chassis) to pin 3 of the output tube with the tube installed and amp on, it will be approx 400 volts DC. Measuring the Plate voltage can be dangerous as it is high voltage, the additional Plate voltage probe is just a safer way to measure the Plate voltage.


Yanno what? I'm sort of skeered of high amps and getting shocked. :shock: Thanks.

I just remembered I work with a EE that plays and say's he has designed and built his own amps. I'm a lab tech and sometimes do work for him. I'm sure he'll fix me up. :lol:

You guys are great. Thanks so much.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Wed Jun 27, 2012 10:12 pm
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The first thing I did was have the bright chip clipped. After a year, I replaced the Jensen with a Celestian, Heritage 30 watt. For me, it was a major improvement! It cranks. Ohhh, and never trust factory biasing, tweaking that tube bias is like a calibration set-up on your guitar.

One last personal peeve is the clip on wires to your speaker. I like to solder them on the posts with silver solder.

Some food for thought.
abako66


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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Thu Jun 28, 2012 3:03 pm
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I just ordered a bias probe. A man can never have too many tools. :lol:

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Thu Jun 28, 2012 3:23 pm
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Be sure to follow the directions for your particular probe. I believe that the inexpensive probe from EuroTubes is different from most other probes (no resistor), in that you connect a current meter to that particular EuroTubes probe, as opposed to a volt meter across the resistor used in most other probes. :idea:

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Thu Jun 28, 2012 3:27 pm
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shimmilou wrote:
Be sure to follow the directions for your particular probe. I believe that the inexpensive probe from EuroTubes is different from most other probes (no resistor), in that you connect a current meter to that particular EuroTubes probe, as opposed to a volt meter across the resistor used in most other probes. :idea:


Thanks. I ordered the one from Amp-Head. Hope I did right.

http://www.amp-head.com/product_info.ph ... ucts_id=30

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Thu Jun 28, 2012 4:07 pm
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Hou-Tex wrote:
shimmilou wrote:
Be sure to follow the directions for your particular probe. I believe that the inexpensive probe from EuroTubes is different from most other probes (no resistor), in that you connect a current meter to that particular EuroTubes probe, as opposed to a volt meter across the resistor used in most other probes. :idea:


Thanks. I ordered the one from Amp-Head. Hope I did right.

http://www.amp-head.com/product_info.ph ... ucts_id=30


You might want to consider canceling or returning that one and order this one instead.

http://www.amp-head.com/product_info.ph ... ucts_id=70

It is the one I use and recommend. A little more expensive, but it allows you to measure cathode current and plate voltage on both tubes. The one you ordered will require you to measure plate voltage at the power tube test point which can be hazardous, unless you ordered it with the plate voltage option. I know from personal experience.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Thu Jun 28, 2012 4:20 pm
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bluesky636 wrote:
Hou-Tex wrote:
shimmilou wrote:
Be sure to follow the directions for your particular probe. I believe that the inexpensive probe from EuroTubes is different from most other probes (no resistor), in that you connect a current meter to that particular EuroTubes probe, as opposed to a volt meter across the resistor used in most other probes. :idea:


Thanks. I ordered the one from Amp-Head. Hope I did right.

http://www.amp-head.com/product_info.ph ... ucts_id=30


You might want to consider canceling or returning that one and order this one instead.

http://www.amp-head.com/product_info.ph ... ucts_id=70

It is the one I use and recommend. A little more expensive, but it allows you to measure cathode current and plate voltage on both tubes. The one you ordered will require you to measure plate voltage at the power tube test point which can be hazardous, unless you ordered it with the plate voltage option. I know from personal experience.



I would agree and was also the one I recommended above in my post.
Both will work fine however..and be careful with either ..we are talking about high voltage. :!:

Best of luck.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Thu Jun 28, 2012 5:04 pm
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Thanks, but I should be ok. The EE I was talking about is going to help me out, he designs and build amps. He even e mailed me the schematics of this amp not that I can read them. In fact he said not to bother with the probe, he uses an O scope and a signal generator.

But, I'm gonna split the difference and do this on my own. Between the amp and another guitar, I really can't afford to spend the extra money when I have the resources to actually help ME out for once! I have an entire lab full of equipment and several double E's that I do testing for including double masters and one PHD.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Thu Jun 28, 2012 5:17 pm
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Hou-Tex wrote:
In fact he said not to bother with the probe, he uses an O scope and a signal generator.


He is using the crossover distortion method of setting bias. You inject a signal into the front of the amp and use the scope to see the crossover distortion where the two halves of the waveform meet. The bias is adjusted until the crossover notch is eliminated. There is a lot of discussion on other forums as to whether this method is better than measuring cathode/plate current and plate voltage. Personally, I think it is not. Bias covers a wide range of values. Once the crossover notch is eliminated there could still be some "wiggle room" in setting the bias. Not to mention the fact that the crossover distortion method requires some complex and expensive equipment.

Here is more info on the method:

http://www.duncanamps.com/technical/scopebias.html

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Thu Jun 28, 2012 6:12 pm
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bluesky636 wrote:
Hou-Tex wrote:
In fact he said not to bother with the probe, he uses an O scope and a signal generator.


He is using the crossover distortion method of setting bias. You inject a signal into the front of the amp and use the scope to see the crossover distortion where the two halves of the waveform meet. The bias is adjusted until the crossover notch is eliminated. There is a lot of discussion on other forums as to whether this method is better than measuring cathode/plate current and plate voltage. Personally, I think it is not. Bias covers a wide range of values. Once the crossover notch is eliminated there could still be some "wiggle room" in setting the bias. Not to mention the fact that the crossover distortion method requires some complex and expensive equipment.

Here is more info on the method:

http://www.duncanamps.com/technical/scopebias.html


To be honest, not sure I trust the guy. It's too close to bedtime to read your link and fully understand it, but I trust you guys. It's too late to cancel my order now, but can I add the other thing next pay day?

Thanks guys.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Thu Jun 28, 2012 7:09 pm
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Hou-Tex wrote:
bluesky636 wrote:
Hou-Tex wrote:
In fact he said not to bother with the probe, he uses an O scope and a signal generator.


He is using the crossover distortion method of setting bias. You inject a signal into the front of the amp and use the scope to see the crossover distortion where the two halves of the waveform meet. The bias is adjusted until the crossover notch is eliminated. There is a lot of discussion on other forums as to whether this method is better than measuring cathode/plate current and plate voltage. Personally, I think it is not. Bias covers a wide range of values. Once the crossover notch is eliminated there could still be some "wiggle room" in setting the bias. Not to mention the fact that the crossover distortion method requires some complex and expensive equipment.

Here is more info on the method:

http://www.duncanamps.com/technical/scopebias.html


To be honest, not sure I trust the guy. It's too close to bedtime to read your link and fully understand it, but I trust you guys. It's too late to cancel my order now, but can I add the other thing next pay day?

Thanks guys.


You never did say which version of the probe you linked to that you bought. If it is just the $30 version, all you can do is measure cathode current and you have to measure plate voltage at the amp test point. If you bought the $50 version it will allow you to measure cathode current and plate voltage using the probe (much safer). But you can only do it for one tube at a time. You need to check both tubes to make sure that they are reasonably balanced and that th eplate voltages on both tubes are close to equal. The version I linked to lets you do all that for both tubes at once.

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