| Author | Message | ||
     Doug Elick |
Some of these questions will be a little off topic, but it's more efficient to post them all at once in a single post... So I just picked up an HD-130 Reverb and matching 212 cab. In reading this site, I've come up with more questions than before I did. 1) It's my understanding that running the HD-130 at half power is a *bad thing* (TM) as it will wear out the power tubes prematurely because the cathode voltage is dropped as well as the B+. Why would a cooler running heater cause this? (BTW, mine is the 2275 chassis with the 12AX7 phase splitter tube). 2) If I want to get more distortion without pissing off the neighbors, is there any detriment to pulling 2 of the tubes besides wearing them asymetrically? (I'd just rotate them in and out from time to time). 3) Isn't there some scenario where the 12AX7 dying can take the power tubes with it by letting the bias run away (and fry them)? 4) This site mentioned that rust on the transformers is a *bad thing* (TM). Aside from 30 years of wear, my amp is free from rust except for a very light coating on the main power transformer. Should I worry about this? What can I do to halt it? 5) Is there any pressing reason to recap the amp if it appears/sounds to be functioning perfectly? 6) I've always fixed minor tears in paper speaker cones with clear fingernail polish. Does this sound reasonable or is there a more preferable fix? 7) How do I get the old (ripped, peeling) Tolex off the cab? What glue is used to hold the replacement on? 8) Can the Bass and Guitar inputs be used at the same time (by a seperate bass and guitar)? 9) Of input 1 and 2, which is the low/high impedance one? 10) The trem and vib. pedal jacks on the back are just make or break circuits (need a simple spst switch), correct? 11) How did I manage to snag such a sweet sounding setup for $250? Thanks, Doug | ||
| Steve Kennedy |
1. On the older models (like yours), going to Low Power selects an alternate tap on the PRIMARY side of the transformer, which cuts every voltage in the amp, including the preamp voltage! I'm not sure about tube life being decreased but this is not as good a solution as what Music Man came up with in the later models, which was cutting the Plate B+ by half and leaving everything else alone. 2. I don't think there would be a problem running only 2 output tubes, as long as you pull the correct ones! I don't think this is going to allow you much volume reduction, it will only cut your headroom. 3. Yes, a hard 12AX7 failure can cause the destruction of the entire output stage under the right set of circumstances. This was the reason the later amps were built with a solid-state phase splitter and many 12AX7 models were updated at the factory when they were returned for warranty repair. 4. Do NOT try to remove rust. Cover it up with a few light coats of Rustoleum or some other similar paint to prevent further deterioration. 5. You will never know you NEED a cap job until fuses blow or you hear hum or audio quality is effected. You will also never know how good the amp can sound unless you do a cap job (unless one has already been performed on your unit). Personally, I don't do one unless an amp just doesn't sound right or otherwise indicates that it needs one. 6. Usually, a white glue is used for speaker repair because it is designed to adhere to paper & wood and is more resilient when dry than fingernail polish. 7. Tolex is removed by heat and/or steam (heat gun and/or Steam Iron). The original glues were made using animal products (usually) so they may give off an interesting smell under these circumstances! Do this with a lot of ventilation or do it outside. I use Dave's Amp Glue, but there are any number of glues sold for this purpose by suppliers of Guitar & amp parts. You can also buy off-the-shelf white contact glue (which is what it is). 8. Yes, but a "shared" amp and speakers don't sound optimum under ANY circumstances! 9. Input 1 is the most sensitive and should be used for a direct connection to a guitar with passive pickups. Input 2 is 2X less sensitive and should be used for active pickups and pedal/effects outputs. Input 2 can also be used to connect to the other channel's Input 1 for playing interesting and useful tricks with the linked tone sections! 10. The Tremelo and Reverb jacks are simple open or closed contacts (just like a standard Fender blackface footswitch). 11. Music Man amps are somewhat undervalued in the market because the collectors haven't caught on yet. We love them for their sound quality and reliability. Give it another 5-10 years and see what happens! Steve |